test(svelte-query/HydrationBoundary): add test for hydrating queries to the cache on context

packages/svelte-query/tests/HydrationBoundary/BaseExample.svelte

@@ -0,0 +1,33 @@
+<script lang="ts">
+  import { QueryClient } from '@tanstack/query-core'
+  import {
+    HydrationBoundary,
+    createQuery,
+    setQueryClientContext,
+  } from '../../src/index.js'
+  import type { DehydratedState } from '@tanstack/query-core'
+
+  let {
+    dehydratedState,
+    queryFn,
+  }: {
+    dehydratedState: DehydratedState
+    queryFn: () => Promise<string>
+  } = $props()
+
+  const queryClient = new QueryClient()
+  setQueryClientContext(queryClient)
+
+  const query = createQuery(() => ({
+    queryKey: ['string'],
+    queryFn,
+  }))
+</script>
+
+<HydrationBoundary
+  state={dehydratedState}
+  options={undefined}
+  queryClient={undefined}
+>
+  <div>data: {query.data ?? 'undefined'}</div>
+</HydrationBoundary>

packages/svelte-query/tests/HydrationBoundary/HydrationBoundary.svelte.test.ts

@@ -0,0 +1,41 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { render } from '@testing-library/svelte'
+import { QueryClient, dehydrate } from '@tanstack/query-core'
+import { sleep } from '@tanstack/query-test-utils'
+import BaseExample from './BaseExample.svelte'
+
+describe('HydrationBoundary', () => {
+  let stringifiedState: string
+
+  beforeEach(async () => {
+    vi.useFakeTimers()
+    const queryClient = new QueryClient()
+    queryClient.prefetchQuery({
+      queryKey: ['string'],
+      queryFn: () => sleep(10).then(() => 'stringCached'),
+    })
+    await vi.advanceTimersByTimeAsync(10)
+    const dehydrated = dehydrate(queryClient)
+    stringifiedState = JSON.stringify(dehydrated)
+    queryClient.clear()
+  })
+
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
+  it('should hydrate queries to the cache on context', async () => {
+    const dehydratedState = JSON.parse(stringifiedState)
+
+    const rendered = render(BaseExample, {
+      props: {
+        dehydratedState,
+        queryFn: () => sleep(20).then(() => 'string'),
+      },
+    })
+
+    expect(rendered.getByText('data: stringCached')).toBeInTheDocument()
+    await vi.advanceTimersByTimeAsync(21)
+    expect(rendered.getByText('data: string')).toBeInTheDocument()
+  })
+})