Fix frame pacing

packages/core/src/runtime.test.ts

@@ -160,6 +160,56 @@ describe('native router transactions', () => {
     expect(native.entries.value.some((entry) => entry.route.path === '/right')).toBe(false)
   })
 
+  it('prepares a newly mounted destination for a paint before animation can begin', async () => {
+    vi.mocked(window.matchMedia).mockReturnValue({ matches: false } as MediaQueryList)
+    let paint: FrameRequestCallback | undefined
+    vi.spyOn(window, 'requestAnimationFrame').mockImplementation((callback) => {
+      paint = callback
+      return 1
+    })
+    const { native } = await harness()
+
+    let resolved = false
+    const beginning = native.beginInteractive('push', '/b').then((id) => {
+      resolved = true
+      return id
+    })
+    await vi.waitFor(() => expect(paint).toBeTypeOf('function'))
+
+    expect(resolved).toBe(false)
+    expect(native.entries.value.find((entry) => entry.route.path === '/b')?.mounted).toBe(true)
+    paint?.(performance.now())
+    expect(await beginning).not.toBeNull()
+    vi.mocked(window.matchMedia).mockReturnValue({ matches: true } as MediaQueryList)
+    await native.cancelInteractive()
+  })
+
+  it('collapses pushed history when a tab replaces it with an existing root', async () => {
+    const { router, native } = await harness()
+    await native.push('/b')
+    expect(native.canGoBack.value).toBe(true)
+
+    await native.sibling('/a', { replace: true })
+
+    expect(router.currentRoute.value.path).toBe('/a')
+    expect(native.canGoBack.value).toBe(false)
+    expect(await native.beginInteractive('pop')).toBeNull()
+  })
+
+  it('manually unloads inactive route instances but never the active view', async () => {
+    const { native } = await harness()
+    await native.replace('/left', { presentation: 'none' })
+    await native.sibling('/middle', { replace: true })
+
+    expect(native.unload('/left')).toBe(1)
+    expect(native.entries.value.find((entry) => entry.route.path === '/left')).toMatchObject({
+      mounted: false,
+      evictionReason: 'manual',
+    })
+    expect(native.unload('/middle')).toBe(0)
+    expect(native.entries.value.find((entry) => entry.route.path === '/middle')?.mounted).toBe(true)
+  })
+
   it('evicts the least-recently-used inactive view when the cache limit is exceeded', async () => {
     let clock = 0
     vi.spyOn(performance, 'now').mockImplementation(() => ++clock)