core/packages/runtime-vapor/__tests__/componentSlots.spec.ts

// NOTE: This test is implemented based on the case of `runtime-core/__test__/componentSlots.spec.ts`.

import {
  VaporTeleport,
  child,
  createComponent,
  createFor,
  createForSlots,
  createIf,
  createSlot,
  createVaporApp,
  defineVaporComponent,
  insert,
  prepend,
  remove,
  renderEffect,
  setInsertionState,
  template,
  txt,
  vaporInteropPlugin,
  withVaporCtx,
} from '../src'
import {
  type Ref,
  createApp,
  createSlots,
  currentInstance,
  h,
  nextTick,
  onScopeDispose,
  ref,
  renderSlot,
  shallowRef,
  toDisplayString,
} from '@vue/runtime-dom'
import { makeRender } from './_utils'
import type { DynamicSlot } from '../src/componentSlots'
import { setElementText, setText } from '../src/dom/prop'
import { isValidBlock } from '../src/block'
import {
  DynamicFragment,
  ForFragment,
  type SlotBoundaryContext,
  SlotFallbackController,
  SlotFragment,
  VaporFragment,
  getCurrentSlotBoundary,
  trackSlotBoundaryDirtying,
  withOwnedSlotBoundary,
  withSlotFallbackBoundary,
} from '../src/fragment'

const define = makeRender<any>()

function renderWithSlots(slots: any): any {
  let instance: any
  const Comp = defineVaporComponent({
    setup() {
      const t0 = template('<div></div>')
      const n0 = t0()
      instance = currentInstance
      return n0
    },
  })

  const { render } = define({
    render() {
      return createComponent(Comp, {}, slots)
    },
  })

  render()
  return instance
}

describe('component: slots', () => {
  test('initSlots: instance.slots should be set correctly', () => {
    const { slots } = renderWithSlots({
      default: () => template('<span></span>')(),
    })

    expect(slots.default()).toMatchObject(document.createElement('span'))
  })

  test('updateSlots: instance.slots should be updated correctly', async () => {
    const flag1 = ref(true)

    let instance: any
    const Child = () => {
      instance = currentInstance
      return template('child')()
    }

    const { render } = define({
      render() {
        return createComponent(
          Child,
          {},
          {
            $: [
              () =>
                flag1.value
                  ? { name: 'one', fn: () => template('<span></span>')() }
                  : { name: 'two', fn: () => template('<div></div>')() },
            ],
          },
        )
      },
    })

    render()

    expect(instance.slots).toHaveProperty('one')
    expect(instance.slots).not.toHaveProperty('two')

    flag1.value = false
    await nextTick()

    expect(instance.slots).not.toHaveProperty('one')
    expect(instance.slots).toHaveProperty('two')
  })

  // passes but no warning for slot invocation in vapor currently
  test.todo('should not warn when mounting another app in setup', () => {
    const Comp = defineVaporComponent({
      setup(_, { slots }) {
        return slots.default!()
      },
    })
    const mountComp = () => {
      createVaporApp({
        render() {
          return createComponent(
            Comp,
            {},
            { default: () => template('msg')() },
          )!
        },
      })
    }
    const App = {
      setup() {
        mountComp()
        return []
      },
    }
    createVaporApp(App).mount(document.createElement('div'))
    expect(
      'Slot "default" invoked outside of the render function',
    ).not.toHaveBeenWarned()
  })

  describe('slot fallback boundary', () => {
    test('slot fragment insert uses active fallback output', () => {
      const container = document.createElement('div')
      const frag = new SlotFragment()

      frag.updateSlot(undefined, () => document.createTextNode('fallback'))

      insert(frag, container)

      expect(container.innerHTML).toBe('fallback<!--slot-->')
    })

    test('slot fragment validity uses active fallback output', () => {
      const frag = new SlotFragment()

      frag.updateSlot(undefined, () => document.createTextNode('fallback'))

      expect(isValidBlock(frag)).toBe(true)
    })

    test('slot fragment remove cleans active fallback and fallback scope', () => {
      const container = document.createElement('div')
      const stop = vi.fn()
      const frag = new SlotFragment()
      frag.updateSlot(undefined, () => {
        onScopeDispose(stop)
        return document.createTextNode('fallback')
      })
      insert(frag, container)
      remove(frag, container)

      expect(Array.from(container.childNodes)).toEqual([])
      expect(stop).toHaveBeenCalledTimes(1)
    })

    test('slot fragment prefers local fallback over inherited fallback', () => {
      const localFallback = vi.fn(() =>
        document.createTextNode('local fallback'),
      )
      const inheritedFallback = vi.fn(() =>
        document.createTextNode('inherited fallback'),
      )
      const frag = new SlotFragment()
      frag.parentSlotBoundary = {
        parent: null,
        getLocalFallback: () => inheritedFallback,
        markDirty: vi.fn(),
      }

      frag.updateSlot(undefined, localFallback)

      expect(frag.fallbackBlock).toBeInstanceOf(Text)
      expect((frag.fallbackBlock as Text).textContent).toBe('local fallback')
      expect(localFallback).toHaveBeenCalled()
      expect(inheritedFallback).not.toHaveBeenCalled()
    })

    test('slot fragment local fallback renders nested slots against the parent boundary', () => {
      const parentBoundary = {
        parent: null,
        getLocalFallback: () => () => document.createTextNode('outer fallback'),
        markDirty: vi.fn(),
      }
      const frag = new SlotFragment()
      frag.parentSlotBoundary = parentBoundary
      let fallbackBoundary: any

      frag.updateSlot(undefined, () => {
        fallbackBoundary = getCurrentSlotBoundary()
        return []
      })

      // Fallback body renders under a redirected boundary whose `.parent` is
      // the owning boundary's parent — so nested slots inherit from the
      // grandparent, avoiding fallback -> <slot> -> same fallback recursion.
      expect(fallbackBoundary).not.toBe(frag.slotFallbackBoundary)
      expect(fallbackBoundary.parent).toBe(parentBoundary)
    })

    test('withSlotFallbackBoundary reuses the same redirected boundary', () => {
      const parentBoundaryA = {
        parent: null,
        getLocalFallback: () => undefined,
        markDirty: vi.fn(),
      }
      const parentBoundaryB = {
        parent: null,
        getLocalFallback: () => undefined,
        markDirty: vi.fn(),
      }
      let activeParent = parentBoundaryA
      const boundary: SlotBoundaryContext = {
        get parent() {
          return activeParent
        },
        getLocalFallback: () => () => document.createTextNode('fallback'),
        markDirty: vi.fn(),
      }
      let firstBoundary!: SlotBoundaryContext | null
      let secondBoundary!: SlotBoundaryContext | null

      withSlotFallbackBoundary(boundary, () => {
        firstBoundary = getCurrentSlotBoundary()
      })

      activeParent = parentBoundaryB

      withSlotFallbackBoundary(boundary, () => {
        secondBoundary = getCurrentSlotBoundary()
      })

      expect(firstBoundary).toBe(secondBoundary)
      expect(firstBoundary!.parent).toBe(parentBoundaryB)
      expect(firstBoundary!.getLocalFallback()).toBeUndefined()
    })

    test('slot fragment local fallback keeps itself as owner for nested fragments', () => {
      const container = document.createElement('div')
      const parentBoundary = {
        parent: null,
        getLocalFallback: () => () => document.createTextNode('outer fallback'),
        markDirty: vi.fn(),
      }
      const frag = new SlotFragment()
      const child = new DynamicFragment('if', false, false)
      let initialized = false

      frag.parentSlotBoundary = parentBoundary
      frag.updateSlot(undefined, () => {
        if (!initialized) {
          initialized = true
          trackSlotBoundaryDirtying(child)
          child.update(() => document.createTextNode('inner fallback'))
        }
        return child
      })
      insert(frag, container)

      expect(container.innerHTML).toBe('inner fallback<!--if--><!--slot-->')

      child.update(() => [])

      expect(container.innerHTML).toBe('outer fallback<!--if--><!--slot-->')
    })

    test('slot fragment local fallback ignores unrelated ancestor fallback refs', async () => {
      const ancestorText = ref('outer fallback')
      const localFallback = vi.fn(() =>
        document.createTextNode('local fallback'),
      )
      const container = document.createElement('div')
      const frag = new SlotFragment()
      const parentBoundary = {
        parent: null,
        getLocalFallback: () => () =>
          document.createTextNode(ancestorText.value),
        markDirty: vi.fn(),
      }
      frag.parentSlotBoundary = parentBoundary

      frag.updateSlot(undefined, localFallback)
      insert(frag, container)
      expect(container.innerHTML).toBe('local fallback<!--slot-->')
      expect(localFallback).toHaveBeenCalledTimes(1)

      ancestorText.value = 'updated outer fallback'
      await nextTick()

      expect(container.innerHTML).toBe('local fallback<!--slot-->')
      expect(localFallback).toHaveBeenCalledTimes(1)
    })

    test('slot fragment activates local fallback while preserving content carrier', () => {
      const container = document.createElement('div')
      const content = new DynamicFragment('if', false, false)
      const frag = new SlotFragment()

      frag.updateSlot(
        () => content,
        () => document.createTextNode('fallback'),
      )
      insert(frag, container)

      expect(container.innerHTML).toBe('fallback<!--if--><!--slot-->')
    })

    test('slot fragment activates local fallback while preserving v-for carrier', () => {
      const container = document.createElement('div')
      const content = new ForFragment([[], document.createComment('for')])
      const frag = new SlotFragment()

      frag.updateSlot(
        () => content,
        () => document.createTextNode('fallback'),
      )
      insert(frag, container)

      expect(container.innerHTML).toBe('fallback<!--for--><!--slot-->')
    })

    test('slot fragment delays fallback activation until pending child validity resolves', () => {
      const container = document.createElement('div')
      const frag = new SlotFragment()
      let child!: VaporFragment

      frag.updateSlot(
        () => {
          child = new VaporFragment([])
          child.validityPending = true
          trackSlotBoundaryDirtying(child)
          return child
        },
        () => document.createTextNode('fallback'),
      )
      insert(frag, container)

      expect(container.innerHTML).toBe('<!--slot-->')

      child.validityPending = false
      child.nodes = []
      child.onUpdated!.forEach(hook => hook())

      expect(container.innerHTML).toBe('fallback<!--slot-->')
    })

    test('slot fallback controller ignores dirty notifications after dispose', () => {
      let disposed = false
      const controller = new SlotFallbackController({
        getParentBoundary: () => null,
        getLocalFallback: () => undefined,
        getContent: () => [],
        getParentNode: () => null,
        getAnchor: () => null,
        runWithRenderCtx: fn => fn(),
        isDisposed: () => disposed,
        onValidityChange: vi.fn(),
      })

      disposed = true
      controller.boundary.markDirty()

      expect(controller.takePendingRecheck()).toBe(false)
    })

    test('slot fallback controller does not accumulate order-sync hooks', async () => {
      const fallback = new VaporFragment([
        document.createTextNode('a'),
        document.createTextNode('b'),
      ])
      const controller = new SlotFallbackController({
        getParentBoundary: () => null,
        getLocalFallback: () => () => fallback,
        getContent: () => [],
        getParentNode: () => null,
        getAnchor: () => null,
        runWithRenderCtx: fn => fn(),
        onValidityChange: vi.fn(),
      })

      controller.recheck()
      expect(fallback.onUpdated).toHaveLength(1)

      controller.syncActiveFallback()
      await nextTick()

      expect(fallback.onUpdated).toHaveLength(1)
    })

    test('slot fallback controller re-syncs the whole carrier block order', async () => {
      const container = document.createElement('div')
      const carrierA = document.createTextNode('x')
      const carrierB = document.createTextNode('y')
      const marker = document.createTextNode('!')
      const slotAnchor = document.createComment('slot')
      const fallback = new VaporFragment([
        document.createTextNode('a'),
        document.createTextNode('b'),
      ])
      const controller = new SlotFallbackController({
        getParentBoundary: () => null,
        getLocalFallback: () => () => fallback,
        getContent: () => [carrierA, carrierB],
        getParentNode: () => container,
        getAnchor: () => slotAnchor,
        runWithRenderCtx: fn => fn(),
        isContentValid: () => false,
        onValidityChange: vi.fn(),
      })

      container.append(carrierA, marker, carrierB, slotAnchor)
      controller.recheck()

      expect(container.innerHTML).toBe('abx!y<!--slot-->')

      controller.syncActiveFallback()
      await nextTick()

      expect(container.innerHTML).toBe('abxy!<!--slot-->')
    })

    test('slot fallback controller defaults to idle when isBusy is omitted', () => {
      const fallback = document.createTextNode('fallback')
      const controller = new SlotFallbackController({
        getParentBoundary: () => null,
        getLocalFallback: () => () => fallback,
        getContent: () => [],
        getParentNode: () => null,
        getAnchor: () => null,
        runWithRenderCtx: fn => fn(),
        onValidityChange: vi.fn(),
      })

      controller.boundary.markDirty()

      expect(controller.getActiveFallback()).toBe(fallback)
    })

    test('vdom slot dirties parent boundary once when content stays valid', async () => {
      const text = ref('A')
      const boundary = {
        parent: null,
        getLocalFallback: () => undefined,
        markDirty: vi.fn(),
      }
      const instance = renderWithSlots({})
      const app = createApp({ render: () => null })
      app.use(vaporInteropPlugin)
      const vapor = (app._context as any).vapor
      const slotsRef = shallowRef({
        default: () => [h('div', text.value)],
      })
      const frag = withOwnedSlotBoundary(boundary, () =>
        vapor.vdomSlot(slotsRef, 'default', {}, instance),
      )
      const host = document.createElement('div')

      insert(frag, host)
      boundary.markDirty.mockClear()

      text.value = 'B'
      await nextTick()

      expect(host.innerHTML).toContain('<div>B</div>')
      expect(boundary.markDirty).toHaveBeenCalledTimes(1)
    })

    test('vdom slot still renders vapor fallback when slot content resolves empty', () => {
      const Child = defineVaporComponent({
        setup() {
          return createSlot('default', null, () => template('child fallback')())
        },
      })
      const root = document.createElement('div')

      createApp({
        render: () =>
          h(Child as any, null, {
            default: () => [],
          }),
      })
        .use(vaporInteropPlugin)
        .mount(root)

      expect(root.innerHTML).toBe('child fallback')
    })
  })

  describe('createSlot', () => {
    test('slot should be rendered correctly', () => {
      const Comp = defineVaporComponent(() => {
        const n0 = template('<div>')()
        insert(createSlot('header'), n0 as any as ParentNode)
        return n0
      })

      const { host } = define(() => {
        return createComponent(Comp, null, {
          header: () => template('header')(),
        })
      }).render()

      expect(host.innerHTML).toBe('<div>header<!--slot--></div>')
    })

    test('slot should be rendered correctly with slot props', async () => {
      const src = ref('header')

      const Comp = defineVaporComponent(() => {
        const n0 = template('<div></div>')()
        insert(
          createSlot('header', { title: () => src.value }),
          n0 as any as ParentNode,
        )
        return n0
      })

      const { host } = define(() => {
        return createComponent(Comp, null, {
          header: props => {
            const el = template('<h1></h1>')()
            renderEffect(() => {
              setElementText(el, props.title)
            })
            return el
          },
        })
      }).render()

      expect(host.innerHTML).toBe('<div><h1>header</h1><!--slot--></div>')

      src.value = 'footer'
      await nextTick()
      expect(host.innerHTML).toBe('<div><h1>footer</h1><!--slot--></div>')
    })

    test('slot props should be isolated per fragment in v-for', async () => {
      const items = ref([0, 1, 2])

      const Child = defineVaporComponent(() => {
        const list = createFor(
          () => items.value,
          for_item0 => {
            const n0 = template('<div></div>')()
            insert(
              createSlot('age-option', { age: () => for_item0.value }),
              n0 as any as ParentNode,
            )
            return n0
          },
        )
        return list
      })

      const { host } = define(() => {
        return createComponent(Child, null, {
          'age-option': (props: any) => {
            const el = template('<span></span>')()
            renderEffect(() => {
              setElementText(el, toDisplayString(props.age))
            })
            return el
          },
        })
      }).render()

      expect(host.innerHTML).toBe(
        '<div><span>0</span><!--slot--></div>' +
          '<div><span>1</span><!--slot--></div>' +
          '<div><span>2</span><!--slot--></div><!--for-->',
      )

      items.value = [3, 4]
      await nextTick()
      expect(host.innerHTML).toBe(
        '<div><span>3</span><!--slot--></div>' +
          '<div><span>4</span><!--slot--></div><!--for-->',
      )
    })

    test('dynamic slot props', async () => {
      let props: any

      const bindObj = ref<Record<string, any>>({ foo: 1, baz: 'qux' })
      const Comp = defineVaporComponent(() =>
        createSlot('default', { $: [() => bindObj.value] }),
      )
      define(() =>
        createComponent(Comp, null, {
          default: (_props: any) => ((props = _props), []),
        }),
      ).render()

      expect(props).toEqual({ foo: 1, baz: 'qux' })

      bindObj.value.foo = 2
      await nextTick()
      expect(props).toEqual({ foo: 2, baz: 'qux' })

      delete bindObj.value.baz
      await nextTick()
      expect(props).toEqual({ foo: 2 })
    })

    test('dynamic slot props with static slot props', async () => {
      let props: any

      const foo = ref(0)
      const bindObj = ref<Record<string, any>>({ foo: 100, baz: 'qux' })
      const Comp = defineVaporComponent(() =>
        createSlot('default', {
          foo: () => foo.value,
          $: [() => bindObj.value],
        }),
      )
      define(() =>
        createComponent(Comp, null, {
          default: (_props: any) => ((props = _props), []),
        }),
      ).render()

      expect(props).toEqual({ foo: 100, baz: 'qux' })

      foo.value = 2
      await nextTick()
      expect(props).toEqual({ foo: 100, baz: 'qux' })

      delete bindObj.value.foo
      await nextTick()
      expect(props).toEqual({ foo: 2, baz: 'qux' })
    })

    test('dynamic slot should be rendered correctly with slot props', async () => {
      const val = ref('header')

      const Comp = defineVaporComponent(() => {
        const n0 = template('<div></div>')()
        prepend(
          n0 as any as ParentNode,
          createSlot('header', { title: () => val.value }),
        )
        return n0
      })

      const { host } = define(() => {
        // dynamic slot
        return createComponent(Comp, null, {
          $: [
            () => ({
              name: 'header',
              fn: (props: any) => {
                const el = template('<h1></h1>')()
                renderEffect(() => {
                  setElementText(el, props.title)
                })
                return el
              },
            }),
          ],
        })
      }).render()

      expect(host.innerHTML).toBe('<div><h1>header</h1><!--slot--></div>')

      val.value = 'footer'
      await nextTick()
      expect(host.innerHTML).toBe('<div><h1>footer</h1><!--slot--></div>')
    })

    test('dynamic slot outlet should be render correctly with slot props', async () => {
      const val = ref('header')

      const Comp = defineVaporComponent(() => {
        const n0 = template('<div></div>')()
        prepend(
          n0 as any as ParentNode,
          createSlot(
            () => val.value, // dynamic slot outlet name
          ),
        )
        return n0
      })

      const { host } = define(() => {
        return createComponent(Comp, null, {
          header: () => template('header')(),
          footer: () => template('footer')(),
        })
      }).render()

      expect(host.innerHTML).toBe('<div>header<!--slot--></div>')

      val.value = 'footer'
      await nextTick()
      expect(host.innerHTML).toBe('<div>footer<!--slot--></div>')
    })

    test('fallback should be render correctly', () => {
      const Comp = defineVaporComponent(() => {
        const n0 = template('<div></div>')()
        insert(
          createSlot('header', undefined, () => template('fallback')()),
          n0 as any as ParentNode,
        )
        return n0
      })

      const { host } = define(() => {
        return createComponent(Comp, {}, {})
      }).render()

      expect(host.innerHTML).toBe('<div>fallback<!--slot--></div>')
    })

    test('dynamic slot should be updated correctly', async () => {
      const flag1 = ref(true)

      const Child = defineVaporComponent(() => {
        const temp0 = template('<p></p>')
        const el0 = temp0()
        const el1 = temp0()
        const slot1 = createSlot('one', null, () => template('one fallback')())
        const slot2 = createSlot('two', null, () => template('two fallback')())
        insert(slot1, el0 as any as ParentNode)
        insert(slot2, el1 as any as ParentNode)
        return [el0, el1]
      })

      const { host } = define(() => {
        return createComponent(Child, null, {
          $: [
            () =>
              flag1.value
                ? {
                    name: 'one',
                    fn: () => template('one content')(),
                  }
                : {
                    name: 'two',
                    fn: () => template('two content')(),
                  },
          ],
        })
      }).render()

      expect(host.innerHTML).toBe(
        '<p>one content<!--slot--></p><p>two fallback<!--slot--></p>',
      )

      flag1.value = false
      await nextTick()

      expect(host.innerHTML).toBe(
        '<p>one fallback<!--slot--></p><p>two content<!--slot--></p>',
      )

      flag1.value = true
      await nextTick()

      expect(host.innerHTML).toBe(
        '<p>one content<!--slot--></p><p>two fallback<!--slot--></p>',
      )
    })

    test('dynamic slot outlet should be updated correctly', async () => {
      const slotOutletName = ref('one')

      const Child = defineVaporComponent(() => {
        const temp0 = template('<p>')
        const el0 = temp0()
        const slot1 = createSlot(
          () => slotOutletName.value,
          undefined,
          () => template('fallback')(),
        )
        insert(slot1, el0 as any as ParentNode)
        return el0
      })

      const { host } = define(() => {
        return createComponent(
          Child,
          {},
          {
            one: () => template('one content')(),
            two: () => template('two content')(),
          },
        )
      }).render()

      expect(host.innerHTML).toBe('<p>one content<!--slot--></p>')

      slotOutletName.value = 'two'
      await nextTick()

      expect(host.innerHTML).toBe('<p>two content<!--slot--></p>')

      slotOutletName.value = 'none'
      await nextTick()

      expect(host.innerHTML).toBe('<p>fallback<!--slot--></p>')
    })

    test('non-exist slot', async () => {
      const Child = defineVaporComponent(() => {
        const el0 = template('<p>')()
        const slot = createSlot('not-exist', undefined)
        insert(slot, el0 as any as ParentNode)
        return el0
      })

      const { host } = define(() => {
        return createComponent(Child)
      }).render()

      expect(host.innerHTML).toBe('<p><!--slot--></p>')
    })

    test('use fallback when inner content changes', async () => {
      const Child = {
        setup() {
          return createSlot('default', null, () =>
            document.createTextNode('fallback'),
          )
        },
      }

      const toggle = ref(true)

      const { html } = define({
        setup() {
          return createComponent(Child, null, {
            default: () => {
              return createIf(
                () => toggle.value,
                () => {
                  return document.createTextNode('content')
                },
              )
            },
          })
        },
      }).render()

      expect(html()).toBe('content<!--if--><!--slot-->')

      toggle.value = false
      await nextTick()
      expect(html()).toBe('fallback<!--if--><!--slot-->')

      toggle.value = true
      await nextTick()
      expect(html()).toBe('content<!--if--><!--slot-->')
    })

    test('use fallback on initial render', async () => {
      const Child = {
        setup() {
          return createSlot('default', null, () =>
            document.createTextNode('fallback'),
          )
        },
      }

      const toggle = ref(false)

      const { html } = define({
        setup() {
          return createComponent(Child, null, {
            default: () => {
              return createIf(
                () => toggle.value,
                () => {
                  return document.createTextNode('content')
                },
              )
            },
          })
        },
      }).render()

      expect(html()).toBe('fallback<!--if--><!--slot-->')

      toggle.value = true
      await nextTick()
      expect(html()).toBe('content<!--if--><!--slot-->')

      toggle.value = false
      await nextTick()
      expect(html()).toBe('fallback<!--if--><!--slot-->')
    })

    test('dynamic slot work with v-if', async () => {
      const val = ref('header')
      const toggle = ref(false)

      const Comp = defineVaporComponent(() => {
        const n0 = template('<div></div>')()
        prepend(n0 as any as ParentNode, createSlot('header', null))
        return n0
      })

      const { host } = define(() => {
        // dynamic slot
        return createComponent(Comp, null, {
          $: [
            () =>
              (toggle.value
                ? {
                    name: val.value,
                    fn: () => {
                      return template('<h1></h1>')()
                    },
                  }
                : void 0) as DynamicSlot,
          ],
        })
      }).render()

      expect(host.innerHTML).toBe('<div><!--slot--></div>')

      toggle.value = true
      await nextTick()
      expect(host.innerHTML).toBe('<div><h1></h1><!--slot--></div>')
    })

    test('slots proxy ownKeys trap correctly reflects dynamic slot presence', async () => {
      const val = ref('header')
      const toggle = ref(false)

      let instance: any
      const Comp = defineVaporComponent(() => {
        instance = currentInstance
        const n0 = template('<div></div>')()
        prepend(n0 as any as ParentNode, createSlot('header', null))
        return n0
      })

      define(() => {
        // dynamic slot
        return createComponent(Comp, null, {
          $: [
            () =>
              (toggle.value
                ? {
                    name: val.value,
                    fn: () => {
                      return template('<h1></h1>')()
                    },
                  }
                : void 0) as DynamicSlot,
          ],
        })
      }).render()

      expect(Reflect.ownKeys(instance.slots)).not.toContain('header')

      toggle.value = true
      await nextTick()
      expect(Reflect.ownKeys(instance.slots)).toContain('header')

      toggle.value = false
      await nextTick()
      expect(Reflect.ownKeys(instance.slots)).not.toContain('header')
    })

    test('render fallback when slot content is not valid', async () => {
      const Child = {
        setup() {
          return createSlot('default', null, () =>
            document.createTextNode('fallback'),
          )
        },
      }

      const { html } = define({
        setup() {
          return createComponent(Child, null, {
            default: () => {
              return template('<!--comment-->')()
            },
          })
        },
      }).render()

      expect(html()).toBe('fallback<!--slot-->')
    })

    test('render fallback when v-if condition is false', async () => {
      const Child = {
        setup() {
          return createSlot('default', null, () =>
            document.createTextNode('fallback'),
          )
        },
      }

      const toggle = ref(false)

      const { html } = define({
        setup() {
          return createComponent(Child, null, {
            default: () => {
              return createIf(
                () => toggle.value,
                () => {
                  return document.createTextNode('content')
                },
              )
            },
          })
        },
      }).render()

      expect(html()).toBe('fallback<!--if--><!--slot-->')

      toggle.value = true
      await nextTick()
      expect(html()).toBe('content<!--if--><!--slot-->')

      toggle.value = false
      await nextTick()
      expect(html()).toBe('fallback<!--if--><!--slot-->')
    })

    test('render fallback with nested v-if', async () => {
      const Child = {
        setup() {
          return createSlot('default', null, () =>
            document.createTextNode('fallback'),
          )
        },
      }

      const outerShow = ref(false)
      const innerShow = ref(false)

      const { html } = define({
        setup() {
          return createComponent(Child, null, {
            default: () => {
              return createIf(
                () => outerShow.value,
                () => {
                  return createIf(
                    () => innerShow.value,
                    () => {
                      return document.createTextNode('content')
                    },
                  )
                },
              )
            },
          })
        },
      }).render()

      expect(html()).toBe('fallback<!--if--><!--slot-->')

      outerShow.value = true
      await nextTick()
      expect(html()).toBe('fallback<!--if--><!--if--><!--slot-->')

      innerShow.value = true
      await nextTick()
      expect(html()).toBe('content<!--if--><!--if--><!--slot-->')

      innerShow.value = false
      await nextTick()
      expect(html()).toBe('fallback<!--if--><!--if--><!--slot-->')

      outerShow.value = false
      await nextTick()
      expect(html()).toBe('fallback<!--if--><!--slot-->')

      outerShow.value = true
      await nextTick()
      expect(html()).toBe('fallback<!--if--><!--if--><!--slot-->')

      innerShow.value = true
      await nextTick()
      expect(html()).toBe('content<!--if--><!--if--><!--slot-->')
    })

    test('render fallback with v-for', async () => {
      const Child = {
        setup() {
          return createSlot('default', null, () =>
            document.createTextNode('fallback'),
          )
        },
      }

      const items = ref<number[]>([1])
      const { html } = define({
        setup() {
          return createComponent(Child, null, {
            default: () => {
              const n2 = createFor(
                () => items.value,
                for_item0 => {
                  const n4 = template('<span> </span>')() as any
                  const x4 = child(n4) as any
                  renderEffect(() =>
                    setText(x4, toDisplayString(for_item0.value)),
                  )
                  return n4
                },
              )
              return n2
            },
          })
        },
      }).render()

      expect(html()).toBe('<span>1</span><!--for--><!--slot-->')

      items.value.pop()
      await nextTick()
      expect(html()).toBe('fallback<!--for--><!--slot-->')

      items.value.pop()
      await nextTick()
      expect(html()).toBe('fallback<!--for--><!--slot-->')

      items.value.push(2)
      await nextTick()
      expect(html()).toBe('<span>2</span><!--for--><!--slot-->')
    })

    test('render fallback with v-for (empty source)', async () => {
      const Child = {
        setup() {
          return createSlot('default', null, () =>
            document.createTextNode('fallback'),
          )
        },
      }

      const items = ref<number[]>([])
      const { html } = define({
        setup() {
          return createComponent(Child, null, {
            default: () => {
              const n2 = createFor(
                () => items.value,
                for_item0 => {
                  const n4 = template('<span> </span>')() as any
                  const x4 = child(n4) as any
                  renderEffect(() =>
                    setText(x4, toDisplayString(for_item0.value)),
                  )
                  return n4
                },
              )
              return n2
            },
          })
        },
      }).render()

      expect(html()).toBe('fallback<!--for--><!--slot-->')

      items.value.push(1)
      await nextTick()
      expect(html()).toBe('<span>1</span><!--for--><!--slot-->')

      items.value.pop()
      await nextTick()
      expect(html()).toBe('fallback<!--for--><!--slot-->')

      items.value.pop()
      await nextTick()
      expect(html()).toBe('fallback<!--for--><!--slot-->')

      items.value.push(2)
      await nextTick()
      expect(html()).toBe('<span>2</span><!--for--><!--slot-->')
    })

    test('render fallback with invalid v-for branch', async () => {
      const Child = {
        setup() {
          return createSlot('default', null, () =>
            document.createTextNode('fallback'),
          )
        },
      }

      const items = ref([{ text: 'bar', show: false }])
      const { html } = define({
        setup() {
          return createComponent(Child, null, {
            default: () => {
              return createFor(
                () => items.value,
                for_item0 => {
                  return createIf(
                    () => for_item0.value.show,
                    () => {
                      const n5 = template('<span> </span>')() as any
                      const x5 = child(n5) as any
                      renderEffect(() =>
                        setText(x5, toDisplayString(for_item0.value.text)),
                      )
                      return n5
                    },
                  )
                },
                item => item.text,
              )
            },
          })
        },
      }).render()

      expect(html()).toBe('fallback<!--if--><!--for--><!--slot-->')

      items.value[0].show = true
      await nextTick()
      expect(html()).toBe('<span>bar</span><!--if--><!--for--><!--slot-->')

      items.value[0].show = false
      await nextTick()
      expect(html()).toBe('fallback<!--if--><!--for--><!--slot-->')
    })

    test('should not render fallback for a single empty item in v-for', async () => {
      const Child = {
        setup() {
          return createSlot('default', null, () =>
            document.createTextNode('fallback'),
          )
        },
      }

      const items = ref([
        { text: 'bar', show: true },
        { text: 'baz', show: true },
      ])
      const { html } = define({
        setup() {
          return createComponent(Child, null, {
            default: () => {
              return createFor(
                () => items.value,
                for_item0 => {
                  return createIf(
                    () => for_item0.value.show,
                    () => {
                      const n5 = template('<span> </span>')() as any
                      const x5 = child(n5) as any
                      renderEffect(() =>
                        setText(x5, toDisplayString(for_item0.value.text)),
                      )
                      return n5
                    },
                  )
                },
                item => item.text,
              )
            },
          })
        },
      }).render()

      expect(html()).toBe(
        '<span>bar</span><!--if--><span>baz</span><!--if--><!--for--><!--slot-->',
      )

      items.value[1].show = false
      await nextTick()
      expect(html()).toBe(
        '<span>bar</span><!--if--><!--if--><!--for--><!--slot-->',
      )
    })

    test('work with v-once', async () => {
      const Child = defineVaporComponent({
        setup() {
          return createSlot(
            'default',
            null,
            undefined,
            undefined,
            true /* once */,
          )
        },
      })

      const count = ref(0)

      const { html } = define({
        setup() {
          return createComponent(Child, null, {
            default: () => {
              const n3 = template('<div> </div>')() as any
              const x3 = txt(n3) as any
              renderEffect(() => setText(x3, toDisplayString(count.value)))
              return n3
            },
          })
        },
      }).render()

      expect(html()).toBe('<div>0</div><!--slot-->')

      // expect no changes due to v-once
      count.value++
      await nextTick()
      expect(html()).toBe('<div>0</div><!--slot-->')
    })
  })

  describe('forwarded slot', () => {
    test('should work', async () => {
      const Child = defineVaporComponent({
        setup() {
          return createSlot('foo', null)
        },
      })
      const Parent = defineVaporComponent({
        setup() {
          const n2 = createComponent(
            Child,
            null,
            {
              foo: withVaporCtx(() => {
                return createSlot('foo', null)
              }),
            },
            true,
          )
          return n2
        },
      })

      const foo = ref('foo')
      const { host } = define({
        setup() {
          const n2 = createComponent(
            Parent,
            null,
            {
              foo: () => {
                const n0 = template(' ')() as any
                renderEffect(() => setText(n0, foo.value))
                return n0
              },
            },
            true,
          )
          return n2
        },
      }).render()

      expect(host.innerHTML).toBe('foo<!--slot--><!--slot-->')

      foo.value = 'bar'
      await nextTick()
      expect(host.innerHTML).toBe('bar<!--slot--><!--slot-->')
    })

    test('mixed with non-forwarded slot', async () => {
      const Child = defineVaporComponent({
        setup() {
          return [createSlot('foo', null)]
        },
      })
      const Parent = defineVaporComponent({
        setup() {
          const n2 = createComponent(Child, null, {
            foo: withVaporCtx(() => {
              const n0 = createSlot('foo', null)
              return n0
            }),
          })
          const n3 = createSlot('default', null)
          return [n2, n3]
        },
      })

      const foo = ref('foo')
      const { host } = define({
        setup() {
          const n2 = createComponent(
            Parent,
            null,
            {
              foo: () => {
                const n0 = template(' ')() as any
                renderEffect(() => setText(n0, foo.value))
                return n0
              },
              default: () => {
                const n3 = template(' ')() as any
                renderEffect(() => setText(n3, foo.value))
                return n3
              },
            },
            true,
          )
          return n2
        },
      }).render()

      expect(host.innerHTML).toBe('foo<!--slot--><!--slot-->foo<!--slot-->')

      foo.value = 'bar'
      await nextTick()
      expect(host.innerHTML).toBe('bar<!--slot--><!--slot-->bar<!--slot-->')
    })

    test('forwarded slot with fallback', async () => {
      const Child = defineVaporComponent({
        setup() {
          return createSlot('default', null, () => template('child fallback')())
        },
      })

      const Parent = defineVaporComponent({
        setup() {
          const n2 = createComponent(Child, null, {
            default: withVaporCtx(() => {
              const n0 = createSlot('default', null, () => {
                return template('<!-- <div></div> -->')()
              })
              return n0
            }),
          })
          return n2
        },
      })

      const { html } = define({
        setup() {
          return createComponent(Parent, null, {
            default: () => template('<!-- <div>App</div> -->')(),
          })
        },
      }).render()

      expect(html()).toBe('child fallback<!--slot--><!--slot-->')
    })

    test('named forwarded slot with v-if', async () => {
      const Child = defineVaporComponent({
        setup() {
          return createSlot('default', null)
        },
      })

      const Parent = defineVaporComponent({
        props: {
          show: Boolean,
        },
        setup(props) {
          const n6 = createComponent(
            Child,
            null,
            {
              default: withVaporCtx(() => {
                const n0 = createIf(
                  () => props.show,
                  () => {
                    const n5 = template('<div></div>')() as any
                    setInsertionState(n5, null, 0, true)
                    createSlot('header', null, () => {
                      const n4 = template('default header')()
                      return n4
                    })
                    return n5
                  },
                )
                return n0
              }),
            },
            true,
          )
          return n6
        },
      })

      const show = ref(false)
      const { html } = define({
        setup() {
          return createComponent(
            Parent,
            {
              show: () => show.value,
            },
            {
              header: () => template('custom header')(),
            },
          )
        },
      }).render()

      expect(html()).toBe('<!--if--><!--slot-->')

      show.value = true
      await nextTick()
      expect(html()).toBe(
        '<div>custom header<!--slot--></div><!--if--><!--slot-->',
      )

      show.value = false
      await nextTick()
      expect(html()).toBe('<!--if--><!--slot-->')
    })

    test('forwarded slot with fallback (v-if)', async () => {
      const Child = defineVaporComponent({
        setup() {
          return createSlot('default', null, () => template('child fallback')())
        },
      })

      const show = ref(false)
      const Parent = defineVaporComponent({
        setup() {
          const n2 = createComponent(Child, null, {
            default: withVaporCtx(() => {
              const n0 = createSlot('default', null, () => {
                const n2 = createIf(
                  () => show.value,
                  () => {
                    const n4 = template('<div>if content</div>')()
                    return n4
                  },
                )
                return n2
              })
              return n0
            }),
          })
          return n2
        },
      })

      const { html } = define({
        setup() {
          return createComponent(Parent, null, {
            default: () => template('<!-- <div>App</div> -->')(),
          })
        },
      }).render()

      expect(html()).toBe('child fallback<!--if--><!--slot--><!--slot-->')

      show.value = true
      await nextTick()
      expect(html()).toBe(
        '<div>if content</div><!--if--><!--slot--><!--slot-->',
      )
    })

    test('forwarded slot with fallback (v-for)', async () => {
      const Child = defineVaporComponent({
        setup() {
          return createSlot('default', null, () => template('child fallback')())
        },
      })

      const items = ref<number[]>([])
      const Parent = defineVaporComponent({
        setup() {
          const n2 = createComponent(Child, null, {
            default: withVaporCtx(() => {
              const n0 = createSlot('default', null, () => {
                const n2 = createFor(
                  () => items.value,
                  for_item0 => {
                    const n4 = template('<span> </span>')() as any
                    const x4 = child(n4) as any
                    renderEffect(() =>
                      setText(x4, toDisplayString(for_item0.value)),
                    )
                    return n4
                  },
                )
                return n2
              })
              return n0
            }),
          })
          return n2
        },
      })

      const { html } = define({
        setup() {
          return createComponent(Parent, null, {
            default: () => template('<!-- <div>App</div> -->')(),
          })
        },
      }).render()

      expect(html()).toBe('child fallback<!--for--><!--slot--><!--slot-->')

      items.value.push(1)
      await nextTick()
      expect(html()).toBe('<span>1</span><!--for--><!--slot--><!--slot-->')

      items.value.pop()
      await nextTick()
      expect(html()).toBe('child fallback<!--for--><!--slot--><!--slot-->')
    })

    test('consecutive slots with insertion state', async () => {
      const { component: Child } = define({
        setup() {
          const n2 = template('<div><div>baz</div></div>', true)() as any
          setInsertionState(n2, 0)
          createSlot('default', null)
          setInsertionState(n2, 0)
          createSlot('foo', null)
          return n2
        },
      })

      const { html } = define({
        setup() {
          return createComponent(Child, null, {
            default: () => template('default')(),
            foo: () => template('foo')(),
          })
        },
      }).render()

      expect(html()).toBe(
        `<div>` +
          `default<!--slot-->` +
          `foo<!--slot-->` +
          `<div>baz</div>` +
          `</div>`,
      )
    })

    describe('vdom interop', () => {
      const createVaporSlot = (fallbackText = 'fallback') => {
        return defineVaporComponent({
          setup() {
            const n0 = createSlot('foo', null, () => {
              const n2 = template(`<div>${fallbackText}</div>`)()
              return n2
            })
            return n0
          },
        })
      }

      const createVdomSlot = (fallbackText = 'fallback') => {
        return {
          render(this: any) {
            return renderSlot(this.$slots, 'foo', {}, () => [
              h('div', fallbackText),
            ])
          },
        }
      }

      const createVaporForwardedSlot = (
        targetComponent: any,
        fallbackText?: string,
      ) => {
        return defineVaporComponent({
          setup() {
            const n2 = createComponent(
              targetComponent,
              null,
              {
                foo: withVaporCtx(() => {
                  return fallbackText
                    ? createSlot('foo', null, () => {
                        const n2 = template(`<div>${fallbackText}</div>`)()
                        return n2
                      })
                    : createSlot('foo', null)
                }),
              },
              true,
            )
            return n2
          },
        })
      }

      const createVdomForwardedSlot = (
        targetComponent: any,
        fallbackText?: string,
      ) => {
        return {
          render(this: any) {
            return h(targetComponent, null, {
              foo: () => [
                fallbackText
                  ? renderSlot(this.$slots, 'foo', {}, () => [
                      h('div', fallbackText),
                    ])
                  : renderSlot(this.$slots, 'foo'),
              ],
              _: 3 /* FORWARDED */,
            })
          },
        }
      }

      const createMultipleVaporForwardedSlots = (
        targetComponent: any,
        count: number,
      ) => {
        let current = targetComponent
        for (let i = 0; i < count; i++) {
          current = createVaporForwardedSlot(current)
        }
        return current
      }

      const createMultipleVdomForwardedSlots = (
        targetComponent: any,
        count: number,
      ) => {
        let current = targetComponent
        for (let i = 0; i < count; i++) {
          current = createVdomForwardedSlot(current)
        }
        return current
      }

      const createTestApp = (
        rootComponent: any,
        foo: Ref<string>,
        show: Ref<boolean>,
      ) => {
        return {
          setup() {
            return () =>
              h(
                rootComponent,
                null,
                createSlots({ _: 2 /* DYNAMIC */ } as any, [
                  show.value
                    ? {
                        name: 'foo',
                        fn: () => [h('span', foo.value)],
                        key: '0',
                      }
                    : undefined,
                ]),
              )
          },
        }
      }

      const createEmptyTestApp = (rootComponent: any) => {
        return {
          setup() {
            return () => h(rootComponent)
          },
        }
      }

      test('vdom slot > vapor forwarded slot > vapor slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VaporForwardedSlot = createVaporForwardedSlot(VaporSlot)
        const App = createTestApp(VaporForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div><!--slot-->')
      })

      test('vdom slot > vapor forwarded slot(with fallback) > vapor slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VaporForwardedSlotWithFallback = createVaporForwardedSlot(
          VaporSlot,
          'forwarded fallback',
        )
        const App = createTestApp(VaporForwardedSlotWithFallback, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>forwarded fallback</div><!--slot-->')
      })

      test('vdom slot > vapor forwarded slot > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()
        const VaporForwardedSlot = createVaporForwardedSlot(VdomSlot)
        const App = createTestApp(VaporForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')
      })

      test('vdom slot > vapor forwarded slot(with fallback) > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()
        const VaporForwardedSlotWithFallback = createVaporForwardedSlot(
          VdomSlot,
          'forwarded fallback',
        )
        const App = createTestApp(VaporForwardedSlotWithFallback, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>forwarded fallback</div>')
      })

      test('vdom slot > vapor forwarded slot > vdom forwarded slot > vapor slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VdomForwardedSlot = createVdomForwardedSlot(VaporSlot)
        const VaporForwardedSlot = createVaporForwardedSlot(VdomForwardedSlot)
        const App = createTestApp(VaporForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')
      })

      test('vdom slot > vapor forwarded slot(with fallback) > vdom forwarded slot > vapor slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VdomForwardedSlot = createVdomForwardedSlot(VaporSlot)
        const VaporForwardedSlotWithFallback = createVaporForwardedSlot(
          VdomForwardedSlot,
          'forwarded fallback',
        )
        const App = createTestApp(VaporForwardedSlotWithFallback, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>forwarded fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')
      })

      test('vdom slot > vapor forwarded slot > vdom forwarded slot(with fallback) > vapor slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VdomForwardedSlotWithFallback = createVdomForwardedSlot(
          VaporSlot,
          'vdom fallback',
        )
        const VaporForwardedSlot = createVaporForwardedSlot(
          VdomForwardedSlotWithFallback,
        )
        const App = createTestApp(VaporForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>vdom fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')
      })

      test('vdom slot(empty) > vapor forwarded slot > vdom forwarded slot(with fallback) > vapor slot', async () => {
        const VaporSlot = createVaporSlot()
        const VdomForwardedSlotWithFallback = createVdomForwardedSlot(
          VaporSlot,
          'vdom fallback',
        )
        const VaporForwardedSlot = createVaporForwardedSlot(
          VdomForwardedSlotWithFallback,
        )
        const App = createEmptyTestApp(VaporForwardedSlot)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>vdom fallback</div>')
      })

      test('vdom forwarded fallback updates existing vapor slot block', async () => {
        const fallbackText = ref('fallback')

        const VdomForwardedSlotWithReactiveFallback = {
          render(this: any) {
            return renderSlot(this.$slots, 'foo', {}, () => [
              h('div', fallbackText.value),
            ])
          },
        }
        const VaporForwardedSlot = createVaporForwardedSlot(
          VdomForwardedSlotWithReactiveFallback,
        )
        const App = createEmptyTestApp(VaporForwardedSlot)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>fallback</div>')

        fallbackText.value = 'updated'
        await nextTick()
        expect(root.innerHTML).toBe('<div>updated</div>')
      })

      test('vdom forwarded fallback updates when fallback function identity changes', async () => {
        const useAlt = ref(false)

        const VdomForwardedSlotWithDynamicFallback = {
          render(this: any) {
            const tag = useAlt.value ? 'p' : 'div'
            const text = useAlt.value ? 'alt fallback' : 'fallback'
            return renderSlot(this.$slots, 'foo', {}, () => [h(tag, text)])
          },
        }
        const VaporForwardedSlot = createVaporForwardedSlot(
          VdomForwardedSlotWithDynamicFallback,
        )
        const App = createEmptyTestApp(VaporForwardedSlot)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>fallback</div>')

        useAlt.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<p>alt fallback</p>')
      })

      test('vdom forwarded fallback identity switch disposes stale fallback effects', async () => {
        const useAlt = ref(false)
        const primaryText = ref('fallback')
        const altText = ref('alt fallback')

        const VdomForwardedSlotWithDynamicFallback = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'foo',
              {},
              useAlt.value
                ? () => [h('p', altText.value)]
                : () => [h('div', primaryText.value)],
            )
          },
        }
        const VaporForwardedSlot = createVaporForwardedSlot(
          VdomForwardedSlotWithDynamicFallback,
        )
        const App = createEmptyTestApp(VaporForwardedSlot)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>fallback</div>')

        useAlt.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<p>alt fallback</p>')

        primaryText.value = 'stale fallback'
        await nextTick()
        expect(root.innerHTML).toBe('<p>alt fallback</p>')

        altText.value = 'active fallback'
        await nextTick()
        expect(root.innerHTML).toBe('<p>active fallback</p>')
      })

      test('vdom fallback updates when renderVaporSlot returns slot fragment', async () => {
        const useAlt = ref(false)

        const VdomSlotWithDynamicFallback = {
          render(this: any) {
            const tag = useAlt.value ? 'p' : 'div'
            const text = useAlt.value ? 'alt fallback' : 'fallback'
            return renderSlot(this.$slots, 'foo', {}, () => [h(tag, text)])
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlotWithDynamicFallback,
              null,
              {
                foo: withVaporCtx(() => createSlot('foo', null)),
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        createVaporApp(VaporForwardedSlot).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>fallback</div><!--slot-->')

        useAlt.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<p>alt fallback</p><!--slot-->')
      })

      test('moving active vdom fallback keeps slot carrier order after teleport move', async () => {
        const targetA = document.createElement('div')
        targetA.id = 'component-slots-fallback-target-a'
        const targetB = document.createElement('div')
        targetB.id = 'component-slots-fallback-target-b'
        document.body.append(targetA, targetB)

        const to = ref('#component-slots-fallback-target-a')
        const fallbackText = ref('fallback')

        try {
          const VdomSlotWithReactiveFallback = {
            render(this: any) {
              return renderSlot(this.$slots, 'foo', {}, () => [
                h('div', fallbackText.value),
              ])
            },
          }

          const VaporTeleportedSlot = defineVaporComponent({
            setup() {
              return createComponent(
                VaporTeleport,
                {
                  to: () => to.value,
                },
                {
                  default: withVaporCtx(() =>
                    createComponent(
                      VdomSlotWithReactiveFallback,
                      null,
                      {
                        foo: withVaporCtx(() => createSlot('foo', null)),
                      },
                      true,
                    ),
                  ),
                },
              )
            },
          })

          const host = document.createElement('div')
          const app = createVaporApp(VaporTeleportedSlot)
          app.use(vaporInteropPlugin)
          app.mount(host)
          await nextTick()

          expect(targetA.innerHTML).toBe('<div>fallback</div><!--slot-->')
          expect(targetB.innerHTML).toBe('')

          to.value = '#component-slots-fallback-target-b'
          await nextTick()

          expect(targetA.innerHTML).toBe('')
          expect(targetB.innerHTML).toBe('<div>fallback</div><!--slot-->')

          fallbackText.value = 'moved fallback'
          await nextTick()

          expect(targetB.innerHTML).toBe('<div>moved fallback</div><!--slot-->')

          app.unmount()
        } finally {
          targetA.remove()
          targetB.remove()
        }
      })

      test('vdom fallback removal clears inherited vapor fallback', async () => {
        const useFallback = ref(true)

        const VdomSlotWithOptionalFallback = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'foo',
              {},
              useFallback.value ? () => [h('div', 'fallback')] : undefined,
            )
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlotWithOptionalFallback,
              null,
              {
                foo: withVaporCtx(() => createSlot('foo', null)),
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        createVaporApp(VaporForwardedSlot).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>fallback</div><!--slot-->')

        useFallback.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<!--slot-->')
      })

      test('vdom fallback can update to empty without crashing', async () => {
        const showFallback = ref(true)

        const VdomSlotWithReactiveFallback = {
          render(this: any) {
            return renderSlot(this.$slots, 'foo', {}, () =>
              showFallback.value ? [h('div', 'fallback')] : [],
            )
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlotWithReactiveFallback,
              null,
              {
                foo: withVaporCtx(() => createSlot('foo', null)),
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        createVaporApp(VaporForwardedSlot).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>fallback</div><!--slot-->')

        showFallback.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<!--slot-->')

        showFallback.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div><!--slot-->')
      })

      test('vdom fallback removal clears active wrapper fallback for non-slot-fragment content', async () => {
        const useFallback = ref(true)

        const VdomSlotWithOptionalFallback = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'foo',
              {},
              useFallback.value ? () => [h('div', 'fallback')] : undefined,
            )
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlotWithOptionalFallback,
              null,
              {
                foo: withVaporCtx(() =>
                  createIf(
                    () => false,
                    () => template('<span>content</span>')(),
                  ),
                ),
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        createVaporApp(VaporForwardedSlot).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>fallback</div><!--if-->')

        useFallback.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<!--if-->')
      })

      test('vdom fallback toggles between local and inherited fallback for non-slot-fragment content', async () => {
        const useFallback = ref(true)
        const VaporSlot = createVaporSlot('outer fallback')

        const VdomForwardedSlotWithOptionalFallback = {
          render(this: any) {
            return h(VaporSlot, null, {
              foo: () => [
                renderSlot(
                  this.$slots,
                  'foo',
                  {},
                  useFallback.value
                    ? () => [h('div', 'local fallback')]
                    : undefined,
                ),
              ],
              _: 3 /* FORWARDED */,
            })
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomForwardedSlotWithOptionalFallback,
              null,
              {
                foo: withVaporCtx(() =>
                  createIf(
                    () => false,
                    () => template('<span>content</span>')(),
                  ),
                ),
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        createVaporApp(VaporForwardedSlot).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>local fallback</div><!--if-->')

        useFallback.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>outer fallback</div><!--if-->')

        useFallback.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<div>local fallback</div><!--if-->')
      })

      test('nested interop vapor slot fallback should satisfy enclosing vapor slot validity after content becomes invalid', async () => {
        const showContent = ref(true)
        const OuterVaporSlot = createVaporSlot('outer fallback')

        const VdomSlotWithLocalFallback = {
          render(this: any) {
            return renderSlot(this.$slots, 'bar', {}, () => [
              h('div', 'local fallback'),
            ])
          },
        }

        const NestedInteropContainer = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlotWithLocalFallback,
              null,
              {
                bar: withVaporCtx(() =>
                  createIf(
                    () => showContent.value,
                    () => template('<span>content</span>')(),
                  ),
                ),
              },
              true,
            )
          },
        })

        const App = defineVaporComponent({
          setup() {
            return createComponent(
              OuterVaporSlot,
              null,
              {
                foo: withVaporCtx(() =>
                  createComponent(NestedInteropContainer, null, null),
                ),
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        createVaporApp(App).use(vaporInteropPlugin).mount(root)
        await nextTick()
        expect(root.innerHTML).toBe('<span>content</span><!--if--><!--slot-->')

        showContent.value = false
        await nextTick()
        expect(root.innerHTML).toBe(
          '<div>local fallback</div><!--if--><!--slot-->',
        )
      })

      test('vdom fallback addition activates inherited vapor fallback', async () => {
        const useFallback = ref(false)

        const VdomSlotWithOptionalFallback = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'foo',
              {},
              useFallback.value ? () => [h('div', 'fallback')] : undefined,
            )
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlotWithOptionalFallback,
              null,
              {
                foo: withVaporCtx(() => createSlot('foo', null)),
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        createVaporApp(VaporForwardedSlot).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<!--slot-->')

        useFallback.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div><!--slot-->')
      })

      test('vdom fallback addition should not remount valid forwarded vapor content', async () => {
        const useFallback = ref(false)
        const mountSpy = vi.fn()

        const Content = defineVaporComponent({
          setup() {
            mountSpy()
            return template('<span>content</span>')()
          },
        })

        const VdomSlotWithOptionalFallback = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'foo',
              {},
              useFallback.value ? () => [h('div', 'fallback')] : undefined,
            )
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlotWithOptionalFallback,
              null,
              {
                foo: withVaporCtx(() => createComponent(Content, null, null)),
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        createVaporApp(VaporForwardedSlot).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>content</span>')
        expect(mountSpy).toHaveBeenCalledTimes(1)

        useFallback.value = true
        await nextTick()

        expect(root.innerHTML).toBe('<span>content</span>')
        expect(mountSpy).toHaveBeenCalledTimes(1)
      })

      test('vdom fallback added over valid forwarded vapor content should activate later when content becomes invalid', async () => {
        const useFallback = ref(false)
        const showContent = ref(true)
        const mountSpy = vi.fn()

        const Content = defineVaporComponent({
          setup() {
            mountSpy()
            return createIf(
              () => showContent.value,
              () => template('<span>content</span>')(),
            )
          },
        })

        const VdomSlotWithOptionalFallback = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'foo',
              {},
              useFallback.value ? () => [h('div', 'fallback')] : undefined,
            )
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlotWithOptionalFallback,
              null,
              {
                foo: withVaporCtx(() => createComponent(Content, null, null)),
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        createVaporApp(VaporForwardedSlot).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>content</span><!--if-->')
        expect(mountSpy).toHaveBeenCalledTimes(1)

        useFallback.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>content</span><!--if-->')
        expect(mountSpy).toHaveBeenCalledTimes(1)

        showContent.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div><!--if-->')
        expect(mountSpy).toHaveBeenCalledTimes(1)
      })

      test('vdom fallback added over forwarded vapor slot fragments should activate when slot content later becomes invalid', async () => {
        const useFallback = ref(false)
        const foo = ref('content')
        const showContent = ref(true)

        const VdomSlotWithOptionalFallback = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'foo',
              {},
              useFallback.value ? () => [h('div', 'fallback')] : undefined,
            )
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlotWithOptionalFallback,
              null,
              {
                foo: withVaporCtx(() => createSlot('foo', null)),
              },
              true,
            )
          },
        })

        const App = createTestApp(VaporForwardedSlot, foo, showContent)
        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>content</span>')

        useFallback.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>content</span>')

        showContent.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div>')
      })

      test('vdom fallback added later should propagate to nested slot boundaries inside still-valid content', async () => {
        const useFallback = ref(false)
        const showInner = ref(true)

        const NestedSlotContainer = defineVaporComponent({
          setup() {
            return [template('<span>stable</span>')(), createSlot('bar', null)]
          },
        })

        const VdomSlotWithOptionalFallback = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'foo',
              {},
              useFallback.value
                ? () => [h('div', 'outer fallback')]
                : undefined,
            )
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlotWithOptionalFallback,
              null,
              {
                foo: withVaporCtx(() =>
                  createComponent(
                    NestedSlotContainer,
                    null,
                    {
                      bar: withVaporCtx(() =>
                        createIf(
                          () => showInner.value,
                          () => template('<i>inner</i>')(),
                        ),
                      ),
                    },
                    true,
                  ),
                ),
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        createVaporApp(VaporForwardedSlot).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe(
          '<span>stable</span><i>inner</i><!--if--><!--slot-->',
        )

        useFallback.value = true
        await nextTick()
        expect(root.innerHTML).toBe(
          '<span>stable</span><i>inner</i><!--if--><!--slot-->',
        )

        showInner.value = false
        await nextTick()
        expect(root.innerHTML).toBe(
          '<span>stable</span><div>outer fallback</div><!--if--><!--slot-->',
        )
      })

      test('vdom fallback toggles should wait for the next nested invalidation inside still-valid content', async () => {
        const useFallback = ref(false)
        const showInner = ref(false)

        const NestedSlotContainer = defineVaporComponent({
          setup() {
            return [template('<span>stable</span>')(), createSlot('bar', null)]
          },
        })

        const VdomSlotWithOptionalFallback = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'foo',
              {},
              useFallback.value
                ? () => [h('div', 'outer fallback')]
                : undefined,
            )
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlotWithOptionalFallback,
              null,
              {
                foo: withVaporCtx(() =>
                  createComponent(
                    NestedSlotContainer,
                    null,
                    {
                      bar: withVaporCtx(() =>
                        createIf(
                          () => showInner.value,
                          () => template('<i>inner</i>')(),
                        ),
                      ),
                    },
                    true,
                  ),
                ),
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        createVaporApp(VaporForwardedSlot).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>stable</span><!--if--><!--slot-->')

        useFallback.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>stable</span><!--if--><!--slot-->')

        showInner.value = true
        await nextTick()
        expect(root.innerHTML).toBe(
          '<span>stable</span><i>inner</i><!--if--><!--slot-->',
        )

        showInner.value = false
        await nextTick()
        expect(root.innerHTML).toBe(
          '<span>stable</span><div>outer fallback</div><!--if--><!--slot-->',
        )
      })

      test('vdom local fallback should expose inherited fallback to nested slot boundaries', async () => {
        const VaporSlot = createVaporSlot('outer fallback')

        const NestedFallbackContainer = defineVaporComponent({
          setup() {
            return [
              template('<span>local stable</span>')(),
              createSlot('bar', null),
            ]
          },
        })

        const VdomForwardedSlotWithNestedFallback = {
          render(this: any) {
            return h(VaporSlot, null, {
              foo: () => [
                renderSlot(this.$slots, 'foo', {}, () => [
                  h(NestedFallbackContainer),
                ]),
              ],
              _: 3 /* FORWARDED */,
            })
          },
        }

        const App = createEmptyTestApp(VdomForwardedSlotWithNestedFallback)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe(
          '<span>local stable</span><div>outer fallback</div>',
        )
      })

      test('vdom local fallback should expose inherited fallback to nested interop vapor slot outlets', async () => {
        const VaporSlot = createVaporSlot('outer fallback')

        const NestedInteropContainer = defineVaporComponent({
          setup() {
            return createSlot('bar', null)
          },
        })
        const localFallback = vi.fn(() => [
          h(NestedInteropContainer, null, {
            baz: () => [h('span', 'unused')],
          }),
        ])

        const VdomForwardedSlotWithNestedInteropFallback = {
          render(this: any) {
            return h(VaporSlot, null, {
              foo: () => [renderSlot(this.$slots, 'foo', {}, localFallback)],
              _: 3 /* FORWARDED */,
            })
          },
        }

        const App = createEmptyTestApp(
          VdomForwardedSlotWithNestedInteropFallback,
        )

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(localFallback).toHaveBeenCalledTimes(1)
        expect(root.textContent).toBe('outer fallback')
      })

      test('vdom local fallback should expose inherited fallback to nested interop vapor forwarded slots', async () => {
        const VaporSlot = createVaporSlot('outer fallback')

        const NestedVdomSlot = {
          render(this: any) {
            return renderSlot(this.$slots, 'bar')
          },
        }

        const NestedInteropForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              NestedVdomSlot,
              null,
              {
                bar: withVaporCtx(() => createSlot('bar', null)),
              },
              true,
            )
          },
        })
        const localFallback = vi.fn(() => [h(NestedInteropForwardedSlot)])

        const VdomForwardedSlotWithNestedInteropFallback = {
          render(this: any) {
            return h(VaporSlot, null, {
              foo: () => [renderSlot(this.$slots, 'foo', {}, localFallback)],
              _: 3 /* FORWARDED */,
            })
          },
        }

        const App = createEmptyTestApp(
          VdomForwardedSlotWithNestedInteropFallback,
        )

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(localFallback).toHaveBeenCalledTimes(1)
        expect(root.textContent).toBe('outer fallback')
      })

      test('vdom local fallback should keep nested inherited vapor fallback reactive after mount', async () => {
        const fallbackText = ref('outer fallback')

        const VaporSlot = defineVaporComponent({
          setup() {
            return createSlot('foo', null, () => {
              const el = template('<div></div>')()
              renderEffect(() => {
                setElementText(el, fallbackText.value)
              })
              return el
            })
          },
        })

        const NestedInteropContainer = defineVaporComponent({
          setup() {
            return createSlot('bar', null)
          },
        })

        const localFallback = vi.fn(() => [
          h(NestedInteropContainer, null, {
            baz: () => [h('span', 'unused')],
          }),
        ])

        const VdomForwardedSlotWithNestedInteropFallback = {
          render(this: any) {
            return h(VaporSlot, null, {
              foo: () => [renderSlot(this.$slots, 'foo', {}, localFallback)],
              _: 3 /* FORWARDED */,
            })
          },
        }

        const App = createEmptyTestApp(
          VdomForwardedSlotWithNestedInteropFallback,
        )

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(localFallback).toHaveBeenCalledTimes(1)
        expect(root.textContent).toBe('outer fallback')

        fallbackText.value = 'updated outer fallback'
        await nextTick()

        expect(root.textContent).toBe('updated outer fallback')
      })

      test('vdom forwarded inherited vapor fallback should clean up old fallback effects', async () => {
        const show = ref(false)
        const fallbackText = ref('fallback')
        const fallbackRuns = vi.fn()

        const VaporSlot = defineVaporComponent({
          setup() {
            return createSlot('foo', null, () => {
              const el = template('<div></div>')()
              renderEffect(() => {
                fallbackRuns()
                setElementText(el, fallbackText.value)
              })
              return el
            })
          },
        })

        const VdomForwardedSlot = {
          render(this: any) {
            return h(VaporSlot, null, {
              foo: () => [renderSlot(this.$slots, 'foo', {}, () => [])],
              _: 3 /* FORWARDED */,
            })
          },
        }

        const App = {
          setup() {
            return () =>
              h(
                VdomForwardedSlot,
                null,
                createSlots({ _: 2 /* DYNAMIC */ } as any, [
                  show.value
                    ? {
                        name: 'foo',
                        fn: () => [h('span', 'content')],
                        key: '0',
                      }
                    : undefined,
                ]),
              )
          },
        }

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>content</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div>')

        const runsBeforeUpdate = fallbackRuns.mock.calls.length
        fallbackText.value = 'updated'
        await nextTick()

        expect(root.innerHTML).toBe('<div>updated</div>')
        expect(fallbackRuns.mock.calls.length - runsBeforeUpdate).toBe(1)
      })

      test('unmounted passthrough vdom fallback should not react to inherited boundary updates', async () => {
        const showInner = ref(true)
        const useOuterFallback = ref(false)
        const localFallbackRuns = vi.fn()

        const InnerVdomSlot = {
          render(this: any) {
            return renderSlot(this.$slots, 'bar', {}, () => {
              localFallbackRuns()
              return [h('div', 'inner fallback')]
            })
          },
        }

        const OuterVdomSlot = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'foo',
              {},
              useOuterFallback.value
                ? () => [h('div', 'outer fallback')]
                : undefined,
            )
          },
        }

        const InnerBridge = defineVaporComponent({
          setup() {
            return createComponent(
              InnerVdomSlot,
              null,
              {
                bar: withVaporCtx(() => createSlot('bar', null)),
              },
              true,
            )
          },
        })

        const OuterBridge = defineVaporComponent({
          setup() {
            return createComponent(
              OuterVdomSlot,
              null,
              {
                foo: withVaporCtx(() => createSlot('foo', null)),
              },
              true,
            )
          },
        })

        const App = {
          setup() {
            return () =>
              h(
                OuterBridge,
                null,
                createSlots({ _: 2 /* DYNAMIC */ } as any, [
                  showInner.value
                    ? {
                        name: 'foo',
                        fn: () => [h(InnerBridge)],
                        key: '0',
                      }
                    : undefined,
                ]),
              )
          },
        }

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>inner fallback</div>')

        showInner.value = false
        await nextTick()
        expect(root.innerHTML).toBe('')

        const runsBefore = localFallbackRuns.mock.calls.length
        useOuterFallback.value = true
        await nextTick()
        useOuterFallback.value = false
        await nextTick()

        expect(localFallbackRuns.mock.calls.length).toBe(runsBefore)
      })

      test('mounted passthrough vdom local fallback ignores unrelated inherited boundary updates', async () => {
        const useOuterFallback = ref(false)
        const localFallbackRuns = vi.fn()

        const InnerVdomSlot = {
          render(this: any) {
            return renderSlot(this.$slots, 'bar', {}, () => {
              localFallbackRuns()
              return [h('div', 'inner fallback')]
            })
          },
        }

        const OuterVdomSlot = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'foo',
              {},
              useOuterFallback.value
                ? () => [h('div', 'outer fallback')]
                : undefined,
            )
          },
        }

        const InnerBridge = defineVaporComponent({
          setup() {
            return createComponent(
              InnerVdomSlot,
              null,
              {
                bar: withVaporCtx(() => createSlot('bar', null)),
              },
              true,
            )
          },
        })

        const OuterBridge = defineVaporComponent({
          setup() {
            return createComponent(
              OuterVdomSlot,
              null,
              {
                foo: withVaporCtx(() => createSlot('foo', null)),
              },
              true,
            )
          },
        })

        const App = {
          setup() {
            return () =>
              h(
                OuterBridge,
                null,
                createSlots({ _: 2 /* DYNAMIC */ } as any, [
                  {
                    name: 'foo',
                    fn: () => [h(InnerBridge)],
                    key: '0',
                  },
                ]),
              )
          },
        }

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>inner fallback</div>')

        const runsBefore = localFallbackRuns.mock.calls.length
        useOuterFallback.value = true
        await nextTick()

        expect(root.innerHTML).toBe('<div>inner fallback</div>')
        expect(localFallbackRuns.mock.calls.length - runsBefore).toBe(0)
      })

      test('failed forwarded vapor slot remount should not keep stale fallback watchers', async () => {
        const values = ref([0])
        const showFallback = ref(false)
        const fallbackRuns = vi.fn()
        const handled = vi.fn()

        const VdomChild = {
          render(this: any) {
            return renderSlot(
              this.$slots,
              'default',
              {},
              showFallback.value
                ? () => {
                    fallbackRuns()
                    return [h('div', 'outer fallback')]
                  }
                : undefined,
            )
          },
        }

        const VaporParent = defineVaporComponent({
          setup() {
            return createComponent(
              VdomChild,
              null,
              {
                $: [
                  () =>
                    createForSlots(values.value, value => ({
                      name: 'default',
                      fn: () => {
                        if (value === 1) {
                          throw new Error('slot boom')
                        }
                        return template('<span>ok</span>')()
                      },
                    })),
                ],
              },
              true,
            )
          },
        })

        const root = document.createElement('div')
        const app = createApp({
          render: () => h(VaporParent as any),
        })
        app.use(vaporInteropPlugin)
        app.config.errorHandler = handled
        app.mount(root)

        expect(root.innerHTML).toBe('<span>ok</span>')

        values.value = [1]
        await nextTick()
        expect(handled).toHaveBeenCalledTimes(1)

        const runsBefore = fallbackRuns.mock.calls.length
        showFallback.value = true
        await nextTick()

        expect(fallbackRuns.mock.calls.length).toBe(runsBefore)
      })

      test('switching vdom fallback identity disposes stale fallback effects', async () => {
        const fallbackA = ref('fallback A')
        const fallbackB = ref('fallback B')
        const useFallbackA = ref(true)

        const VaporSlot = defineVaporComponent({
          setup() {
            return createSlot('foo', null) as any
          },
        })

        const VdomForwardedSlotWithDynamicFallback = {
          render(this: any) {
            return h(VaporSlot as any, null, {
              foo: () => [
                renderSlot(
                  this.$slots,
                  'foo',
                  {},
                  useFallbackA.value
                    ? () => [h('div', fallbackA.value)]
                    : () => [h('div', fallbackB.value)],
                ),
              ],
              _: 3 /* FORWARDED */,
            })
          },
        }

        const VaporForwardedSlot = createVaporForwardedSlot(
          VdomForwardedSlotWithDynamicFallback,
        )
        const App = createEmptyTestApp(VaporForwardedSlot)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<div>fallback A</div>')

        fallbackA.value = 'fallback A updated'
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback A updated</div>')

        useFallbackA.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback B</div>')

        fallbackA.value = 'stale fallback A'
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback B</div>')

        fallbackB.value = 'fallback B updated'
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback B updated</div>')
      })

      test('vdom slot does not evaluate fallback while forwarded vapor content resolves valid output', () => {
        const fallback = vi.fn(() => [h('div', 'fallback')])

        const VdomSlot = {
          render(this: any) {
            return renderSlot(this.$slots, 'foo', {}, fallback)
          },
        }

        const VaporForwardedSlot = defineVaporComponent({
          setup() {
            return createComponent(
              VdomSlot,
              null,
              {
                foo: withVaporCtx(() =>
                  createIf(
                    () => true,
                    () => template('<span>content</span>')(),
                  ),
                ),
              },
              true,
            )
          },
        })

        const App = createEmptyTestApp(VaporForwardedSlot)
        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)

        expect(root.textContent).toBe('content')
        expect(fallback).not.toHaveBeenCalled()
      })

      test('vdom slot > vapor forwarded slot > vdom forwarded slot > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()
        const VdomForwardedSlot = createVdomForwardedSlot(VdomSlot)
        const VaporForwardedSlot = createVaporForwardedSlot(VdomForwardedSlot)
        const App = createTestApp(VaporForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')
      })

      test('vdom slot > vapor forwarded slot(with fallback) > vdom forwarded slot > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()
        const VdomForwardedSlot = createVdomForwardedSlot(VdomSlot)
        const VaporForwardedSlotWithFallback = createVaporForwardedSlot(
          VdomForwardedSlot,
          'vapor fallback',
        )
        const App = createTestApp(VaporForwardedSlotWithFallback, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>vapor fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')
      })

      test('vdom slot > vapor forwarded slot > vdom forwarded slot(with fallback) > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()

        const VdomForwardedSlotWithFallback = createVdomForwardedSlot(
          VdomSlot,
          'vdom fallback',
        )
        const VaporForwardedSlot = createVaporForwardedSlot(
          VdomForwardedSlotWithFallback,
        )
        const App = createTestApp(VaporForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>vdom fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')
      })

      test('vdom slot > vapor forwarded slot (multiple) > vdom forwarded slot > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()
        const VdomForwardedSlot = createVdomForwardedSlot(VdomSlot)
        const VaporForwardedSlot = createMultipleVaporForwardedSlots(
          VdomForwardedSlot,
          3,
        )
        const App = createTestApp(VaporForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot--><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot--><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div><!--slot--><!--slot-->')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot--><!--slot-->')
      })

      test('vdom slot > vapor forwarded slot (multiple) > vdom forwarded slot(with fallback) > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()
        const VdomForwardedSlotWithFallback = createVdomForwardedSlot(
          VdomSlot,
          'vdom fallback',
        )
        const VaporForwardedSlot = createMultipleVaporForwardedSlots(
          VdomForwardedSlotWithFallback,
          3,
        )
        const App = createTestApp(VaporForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot--><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot--><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe(
          '<div>vdom fallback</div><!--slot--><!--slot-->',
        )

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot--><!--slot-->')
      })

      test('vdom slot > vdom forwarded slot > vapor slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VdomForwardedSlot = createVdomForwardedSlot(VaporSlot)
        const App = createTestApp(VdomForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')
      })

      test('vdom slot > vdom forwarded slot > vapor forwarded slot > vapor slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VaporForwardedSlot = createVaporForwardedSlot(VaporSlot)
        const VdomForwardedSlot = createVdomForwardedSlot(VaporForwardedSlot)
        const App = createTestApp(VdomForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div><!--slot-->')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')
      })

      test('vdom slot > vdom forwarded slot (multiple) > vapor forwarded slot > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VaporForwardedSlot = createVaporForwardedSlot(VaporSlot)
        const VdomForwardedSlot = createMultipleVdomForwardedSlots(
          VaporForwardedSlot,
          3,
        )
        const App = createTestApp(VdomForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div><!--slot-->')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')
      })

      test('vdom slot > vdom forwarded slot (multiple) > vapor forwarded slot(with fallback) > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VaporForwardedSlot = createVaporForwardedSlot(
          VaporSlot,
          'vapor fallback',
        )
        const VdomForwardedSlot = createMultipleVdomForwardedSlots(
          VaporForwardedSlot,
          3,
        )
        const App = createTestApp(VdomForwardedSlot, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>vapor fallback</div><!--slot-->')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')
      })

      test('vdom slot > vapor forwarded slot > vapor forwarded slot > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()
        const VaporForwardedSlot1 = createMultipleVaporForwardedSlots(
          VdomSlot,
          2,
        )
        const App = createTestApp(VaporForwardedSlot1, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div><!--slot-->')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')
      })

      test('vdom slot > vapor forwarded slot(with fallback) > vapor forwarded slot > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()
        const VaporForwardedSlot2 = createVaporForwardedSlot(VdomSlot)
        const VaporForwardedSlot1WithFallback = createVaporForwardedSlot(
          VaporForwardedSlot2,
          'vapor1 fallback',
        )
        const App = createTestApp(VaporForwardedSlot1WithFallback, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>vapor1 fallback</div><!--slot-->')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')
      })

      test('vdom slot > vapor forwarded slot > vapor forwarded slot(with fallback) > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()
        const VaporForwardedSlot2WithFallback = createVaporForwardedSlot(
          VdomSlot,
          'vapor2 fallback',
        )
        const VaporForwardedSlot1 = createVaporForwardedSlot(
          VaporForwardedSlot2WithFallback,
        )
        const App = createTestApp(VaporForwardedSlot1, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>vapor2 fallback</div><!--slot-->')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')
      })

      test('vdom slot > vapor forwarded slot > vapor forwarded slot > vapor slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VaporForwardedSlot2 = createVaporForwardedSlot(VaporSlot)
        const VaporForwardedSlot1 =
          createVaporForwardedSlot(VaporForwardedSlot2)
        const App = createTestApp(VaporForwardedSlot1, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot--><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot--><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>fallback</div><!--slot--><!--slot-->')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot--><!--slot-->')
      })

      test('vdom slot > vapor forwarded slot(with fallback) > vapor forwarded slot(with fallback) > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()
        const VaporForwardedSlot2WithFallback = createVaporForwardedSlot(
          VdomSlot,
          'vapor2 fallback',
        )
        const VaporForwardedSlot1WithFallback = createVaporForwardedSlot(
          VaporForwardedSlot2WithFallback,
          'vapor1 fallback',
        )
        const App = createTestApp(VaporForwardedSlot1WithFallback, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>vapor1 fallback</div><!--slot-->')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot-->')
      })

      test('vdom slot > vapor forwarded slot(with fallback) > vapor forwarded slot(with fallback) > vapor slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VaporForwardedSlot2WithFallback = createVaporForwardedSlot(
          VaporSlot,
          'vapor2 fallback',
        )
        const VaporForwardedSlot1WithFallback = createVaporForwardedSlot(
          VaporForwardedSlot2WithFallback,
          'vapor1 fallback',
        )
        const App = createTestApp(VaporForwardedSlot1WithFallback, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span><!--slot--><!--slot-->')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot--><!--slot-->')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe(
          '<div>vapor1 fallback</div><!--slot--><!--slot-->',
        )

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span><!--slot--><!--slot-->')
      })

      test('vdom slot > vdom forwarded slot(with fallback) > vdom forwarded slot(with fallback) > vapor slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VdomForwardedSlot2WithFallback = createVdomForwardedSlot(
          VaporSlot,
          'vdom2 fallback',
        )
        const VdomForwardedSlot1WithFallback = createVdomForwardedSlot(
          VdomForwardedSlot2WithFallback,
          'vdom1 fallback',
        )
        const App = createTestApp(VdomForwardedSlot1WithFallback, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>vdom1 fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')
      })

      test('vdom slot > vdom forwarded slot(with fallback) > vdom forwarded slot(with fallback) > vdom slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VdomSlot = createVdomSlot()
        const VdomForwardedSlot2WithFallback = createVdomForwardedSlot(
          VdomSlot,
          'vdom2 fallback',
        )
        const VdomForwardedSlot1WithFallback = createVdomForwardedSlot(
          VdomForwardedSlot2WithFallback,
          'vdom1 fallback',
        )
        const App = createTestApp(VdomForwardedSlot1WithFallback, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>vdom1 fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')
      })

      test('vdom slot > vdom forwarded slot(with fallback) > vdom forwarded slot(with fallback) (multiple) > vapor slot', async () => {
        const foo = ref('foo')
        const show = ref(true)

        const VaporSlot = createVaporSlot()
        const VdomForwardedSlot3WithFallback = createVdomForwardedSlot(
          VaporSlot,
          'vdom3 fallback',
        )
        const VdomForwardedSlot2WithFallback = createVdomForwardedSlot(
          VdomForwardedSlot3WithFallback,
          'vdom2 fallback',
        )
        const VdomForwardedSlot1WithFallback = createVdomForwardedSlot(
          VdomForwardedSlot2WithFallback,
          'vdom1 fallback',
        )
        const App = createTestApp(VdomForwardedSlot1WithFallback, foo, show)

        const root = document.createElement('div')
        createApp(App).use(vaporInteropPlugin).mount(root)
        expect(root.innerHTML).toBe('<span>foo</span>')

        foo.value = 'bar'
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')

        show.value = false
        await nextTick()
        expect(root.innerHTML).toBe('<div>vdom1 fallback</div>')

        show.value = true
        await nextTick()
        expect(root.innerHTML).toBe('<span>bar</span>')
      })
    })
  })

  describe('createForSlots', () => {
    test('should work', async () => {
      const loop = ref([1, 2, 3])

      let instance: any
      const Child = () => {
        instance = currentInstance
        return template('child')()
      }

      const { render } = define({
        setup() {
          return createComponent(Child, null, {
            $: [
              () =>
                createForSlots(loop.value, (item, i) => ({
                  name: item,
                  fn: () => template(item + i)(),
                })),
            ],
          })
        },
      })
      render()

      expect(instance.slots).toHaveProperty('1')
      expect(instance.slots).toHaveProperty('2')
      expect(instance.slots).toHaveProperty('3')
      loop.value.push(4)
      await nextTick()
      expect(instance.slots).toHaveProperty('4')
      loop.value.shift()
      await nextTick()
      expect(instance.slots).not.toHaveProperty('1')
    })

    test('should cache dynamic slot source result', async () => {
      const items = ref([1, 2, 3])
      let callCount = 0

      const getItems = () => {
        callCount++
        return items.value
      }

      let instance: any
      const Child = defineVaporComponent(() => {
        instance = currentInstance
        // Create multiple slots to trigger multiple getSlot calls
        const n1 = template('<div></div>')()
        const n2 = template('<div></div>')()
        const n3 = template('<div></div>')()
        insert(createSlot('slot1'), n1 as any as ParentNode)
        insert(createSlot('slot2'), n2 as any as ParentNode)
        insert(createSlot('slot3'), n3 as any as ParentNode)
        return [n1, n2, n3]
      })

      define({
        setup() {
          return createComponent(Child, null, {
            $: [
              () =>
                createForSlots(getItems(), (item, i) => ({
                  name: 'slot' + item,
                  fn: () => template(String(item))(),
                })),
            ],
          })
        },
      }).render()

      // getItems should only be called once
      expect(callCount).toBe(1)

      expect(instance.slots).toHaveProperty('slot1')
      expect(instance.slots).toHaveProperty('slot2')
      expect(instance.slots).toHaveProperty('slot3')
    })

    test('should update when source changes', async () => {
      const items = ref([1, 2])
      let callCount = 0

      const getItems = () => {
        callCount++
        return items.value
      }

      let instance: any
      const Child = defineVaporComponent(() => {
        instance = currentInstance
        const n1 = template('<div></div>')()
        const n2 = template('<div></div>')()
        const n3 = template('<div></div>')()
        insert(createSlot('slot1'), n1 as any as ParentNode)
        insert(createSlot('slot2'), n2 as any as ParentNode)
        insert(createSlot('slot3'), n3 as any as ParentNode)
        return [n1, n2, n3]
      })

      define({
        setup() {
          return createComponent(Child, null, {
            $: [
              () =>
                createForSlots(getItems(), (item, i) => ({
                  name: 'slot' + item,
                  fn: () => template(String(item))(),
                })),
            ],
          })
        },
      }).render()

      expect(callCount).toBe(1)
      expect(instance.slots).toHaveProperty('slot1')
      expect(instance.slots).toHaveProperty('slot2')
      expect(instance.slots).not.toHaveProperty('slot3')

      // Update items
      items.value.push(3)
      await nextTick()

      // Should be called again after source changes
      expect(callCount).toBe(2)
      expect(instance.slots).toHaveProperty('slot1')
      expect(instance.slots).toHaveProperty('slot2')
      expect(instance.slots).toHaveProperty('slot3')
    })

    test('should render slots correctly with caching', async () => {
      const items = ref([1, 2, 3, 4, 5])

      const Child = defineVaporComponent(() => {
        const containers: any[] = []
        for (let i = 1; i <= 5; i++) {
          const n = template('<div></div>')()
          insert(createSlot('slot' + i), n as any as ParentNode)
          containers.push(n)
        }
        return containers
      })

      const { host } = define({
        setup() {
          return createComponent(Child, null, {
            $: [
              () =>
                createForSlots(items.value, item => ({
                  name: 'slot' + item,
                  fn: () => template('content' + item)(),
                })),
            ],
          })
        },
      }).render()

      expect(host.innerHTML).toBe(
        '<div>content1<!--slot--></div>' +
          '<div>content2<!--slot--></div>' +
          '<div>content3<!--slot--></div>' +
          '<div>content4<!--slot--></div>' +
          '<div>content5<!--slot--></div>',
      )

      // Update items
      items.value = [2, 4]
      await nextTick()

      expect(host.innerHTML).toBe(
        '<div><!--slot--></div>' +
          '<div>content2<!--slot--></div>' +
          '<div><!--slot--></div>' +
          '<div>content4<!--slot--></div>' +
          '<div><!--slot--></div>',
      )
    })

    // #14648
    test('should use last slot when v-for generates duplicate slot names', async () => {
      const list = ref([0, 1, 2])

      const Child = defineVaporComponent(() => {
        const n = template('<div></div>')()
        insert(createSlot('default'), n as any as ParentNode)
        return n
      })

      const { host } = define({
        setup() {
          return createComponent(Child, null, {
            $: [
              () =>
                createForSlots(list.value, item => ({
                  name: 'default',
                  fn: () => template(String(item))(),
                })),
            ],
          })
        },
      }).render()

      // should display the last item (last wins, matching vDOM behavior)
      expect(host.innerHTML).toBe('<div>2<!--slot--></div>')

      // push: new last item should be displayed
      list.value.push(3)
      await nextTick()
      expect(host.innerHTML).toBe('<div>3<!--slot--></div>')

      // pop: should fall back to previous last item
      list.value.pop()
      await nextTick()
      expect(host.innerHTML).toBe('<div>2<!--slot--></div>')

      // splice middle: last item unchanged
      list.value.splice(1, 1)
      await nextTick()
      expect(host.innerHTML).toBe('<div>2<!--slot--></div>')
    })

    test('should work with null and undefined', async () => {
      const loop = ref<number[] | null | undefined>(undefined)

      let instance: any
      const Child = () => {
        instance = currentInstance
        return template('child')()
      }

      const { render } = define({
        setup() {
          return createComponent(Child, null, {
            $: [
              () =>
                createForSlots(loop.value as any, (item, i) => ({
                  name: item,
                  fn: () => template(item + i)(),
                })),
            ],
          })
        },
      })
      render()

      expect(instance.slots).toEqual({})
      loop.value = [1]
      await nextTick()
      expect(instance.slots).toHaveProperty('1')
      loop.value = null
      await nextTick()
      expect(instance.slots).toEqual({})
    })
  })
})