From fdcf33131dc6f9873e066d12d994fe898d23416a Mon Sep 17 00:00:00 2001
From: Wonsuk Choi <sukvvon@gmail.com>
Date: Sat, 18 Jul 2026 21:50:08 +0900
Subject: [PATCH 1/2] test({react,preact}-query/usePrefetchQuery): inline the
 'generateQueryFn' factory into each call site

---
 .../src/__tests__/usePrefetchQuery.test.tsx   | 29 ++++++++++---------
 .../src/__tests__/usePrefetchQuery.test.tsx   | 29 ++++++++++---------
 2 files changed, 30 insertions(+), 28 deletions(-)

diff --git a/packages/preact-query/src/__tests__/usePrefetchQuery.test.tsx b/packages/preact-query/src/__tests__/usePrefetchQuery.test.tsx
index d05b24a7bc..725a5cfc2c 100644
--- a/packages/preact-query/src/__tests__/usePrefetchQuery.test.tsx
+++ b/packages/preact-query/src/__tests__/usePrefetchQuery.test.tsx
@@ -14,11 +14,6 @@ import {
 import { ErrorBoundary } from './ErrorBoundary'
 import { renderWithClient } from './utils'
 
-const generateQueryFn = (data: string) =>
-  vi
-    .fn<(...args: Array<any>) => Promise<string>>()
-    .mockImplementation(() => sleep(10).then(() => data))
-
 describe('usePrefetchQuery', () => {
   let queryCache: QueryCache
   let queryClient: QueryClient
@@ -37,12 +32,12 @@ describe('usePrefetchQuery', () => {
   it('should prefetch query if query state does not exist', async () => {
     const queryOpts = {
       queryKey: queryKey(),
-      queryFn: generateQueryFn('prefetchQuery'),
+      queryFn: vi.fn(() => sleep(10).then(() => 'prefetchQuery')),
     }
 
     const componentQueryOpts = {
       ...queryOpts,
-      queryFn: generateQueryFn('useSuspenseQuery'),
+      queryFn: vi.fn(() => sleep(10).then(() => 'useSuspenseQuery')),
     }
 
     function Page() {
@@ -72,7 +67,9 @@ describe('usePrefetchQuery', () => {
   it('should not prefetch query if query state exists', async () => {
     const queryOpts = {
       queryKey: queryKey(),
-      queryFn: generateQueryFn('The usePrefetchQuery hook is smart!'),
+      queryFn: vi.fn(() =>
+        sleep(10).then(() => 'The usePrefetchQuery hook is smart!'),
+      ),
     }
 
     function Page() {
@@ -105,7 +102,7 @@ describe('usePrefetchQuery', () => {
   it('should let errors fall through and not refetch failed queries', async () => {
     const consoleMock = vi.spyOn(console, 'error')
     consoleMock.mockImplementation(() => undefined)
-    const queryFn = generateQueryFn('Not an error')
+    const queryFn = vi.fn(() => sleep(10).then(() => 'Not an error'))
 
     const queryOpts = {
       queryKey: queryKey(),
@@ -148,7 +145,7 @@ describe('usePrefetchQuery', () => {
   })
 
   it('should not create an endless loop when using inside a suspense boundary', async () => {
-    const queryFn = generateQueryFn('prefetchedQuery')
+    const queryFn = vi.fn(() => sleep(10).then(() => 'prefetchedQuery'))
 
     const queryOpts = {
       queryKey: queryKey(),
@@ -184,7 +181,9 @@ describe('usePrefetchQuery', () => {
   it('should be able to recover from errors and try fetching again', async () => {
     const consoleMock = vi.spyOn(console, 'error')
     consoleMock.mockImplementation(() => undefined)
-    const queryFn = generateQueryFn('This is fine :dog: :fire:')
+    const queryFn = vi.fn(() =>
+      sleep(10).then(() => 'This is fine :dog: :fire:'),
+    )
 
     const queryOpts = {
       queryKey: queryKey(),
@@ -242,17 +241,19 @@ describe('usePrefetchQuery', () => {
   it('should not create a suspense waterfall if prefetch is fired', async () => {
     const firstQueryOpts = {
       queryKey: queryKey(),
-      queryFn: generateQueryFn('Prefetch is nice!'),
+      queryFn: vi.fn(() => sleep(10).then(() => 'Prefetch is nice!')),
     }
 
     const secondQueryOpts = {
       queryKey: queryKey(),
-      queryFn: generateQueryFn('Prefetch is really nice!!'),
+      queryFn: vi.fn(() => sleep(10).then(() => 'Prefetch is really nice!!')),
     }
 
     const thirdQueryOpts = {
       queryKey: queryKey(),
-      queryFn: generateQueryFn('Prefetch does not create waterfalls!!'),
+      queryFn: vi.fn(() =>
+        sleep(10).then(() => 'Prefetch does not create waterfalls!!'),
+      ),
     }
 
     const Fallback = vi.fn().mockImplementation(() => <div>Loading...</div>)
diff --git a/packages/react-query/src/__tests__/usePrefetchQuery.test.tsx b/packages/react-query/src/__tests__/usePrefetchQuery.test.tsx
index bef84167b4..42bdb44e68 100644
--- a/packages/react-query/src/__tests__/usePrefetchQuery.test.tsx
+++ b/packages/react-query/src/__tests__/usePrefetchQuery.test.tsx
@@ -12,11 +12,6 @@ import {
 } from '..'
 import { renderWithClient } from './utils'
 
-const generateQueryFn = (data: string) =>
-  vi
-    .fn<(...args: Array<any>) => Promise<string>>()
-    .mockImplementation(() => sleep(10).then(() => data))
-
 describe('usePrefetchQuery', () => {
   let queryCache: QueryCache
   let queryClient: QueryClient
@@ -35,12 +30,12 @@ describe('usePrefetchQuery', () => {
   it('should prefetch query if query state does not exist', async () => {
     const queryOpts = {
       queryKey: queryKey(),
-      queryFn: generateQueryFn('prefetchQuery'),
+      queryFn: vi.fn(() => sleep(10).then(() => 'prefetchQuery')),
     }
 
     const componentQueryOpts = {
       ...queryOpts,
-      queryFn: generateQueryFn('useSuspenseQuery'),
+      queryFn: vi.fn(() => sleep(10).then(() => 'useSuspenseQuery')),
     }
 
     function Page() {
@@ -70,7 +65,9 @@ describe('usePrefetchQuery', () => {
   it('should not prefetch query if query state exists', async () => {
     const queryOpts = {
       queryKey: queryKey(),
-      queryFn: generateQueryFn('The usePrefetchQuery hook is smart!'),
+      queryFn: vi.fn(() =>
+        sleep(10).then(() => 'The usePrefetchQuery hook is smart!'),
+      ),
     }
 
     function Page() {
@@ -103,7 +100,7 @@ describe('usePrefetchQuery', () => {
   it('should let errors fall through and not refetch failed queries', async () => {
     const consoleMock = vi.spyOn(console, 'error')
     consoleMock.mockImplementation(() => undefined)
-    const queryFn = generateQueryFn('Not an error')
+    const queryFn = vi.fn(() => sleep(10).then(() => 'Not an error'))
 
     const queryOpts = {
       queryKey: queryKey(),
@@ -146,7 +143,7 @@ describe('usePrefetchQuery', () => {
   })
 
   it('should not create an endless loop when using inside a suspense boundary', async () => {
-    const queryFn = generateQueryFn('prefetchedQuery')
+    const queryFn = vi.fn(() => sleep(10).then(() => 'prefetchedQuery'))
 
     const queryOpts = {
       queryKey: queryKey(),
@@ -182,7 +179,9 @@ describe('usePrefetchQuery', () => {
   it('should be able to recover from errors and try fetching again', async () => {
     const consoleMock = vi.spyOn(console, 'error')
     consoleMock.mockImplementation(() => undefined)
-    const queryFn = generateQueryFn('This is fine :dog: :fire:')
+    const queryFn = vi.fn(() =>
+      sleep(10).then(() => 'This is fine :dog: :fire:'),
+    )
 
     const queryOpts = {
       queryKey: queryKey(),
@@ -240,17 +239,19 @@ describe('usePrefetchQuery', () => {
   it('should not create a suspense waterfall if prefetch is fired', async () => {
     const firstQueryOpts = {
       queryKey: queryKey(),
-      queryFn: generateQueryFn('Prefetch is nice!'),
+      queryFn: vi.fn(() => sleep(10).then(() => 'Prefetch is nice!')),
     }
 
     const secondQueryOpts = {
       queryKey: queryKey(),
-      queryFn: generateQueryFn('Prefetch is really nice!!'),
+      queryFn: vi.fn(() => sleep(10).then(() => 'Prefetch is really nice!!')),
     }
 
     const thirdQueryOpts = {
       queryKey: queryKey(),
-      queryFn: generateQueryFn('Prefetch does not create waterfalls!!'),
+      queryFn: vi.fn(() =>
+        sleep(10).then(() => 'Prefetch does not create waterfalls!!'),
+      ),
     }
 
     const Fallback = vi.fn().mockImplementation(() => <div>Loading...</div>)

From fdd34ca092094a625a4e35828a2894376e61d96a Mon Sep 17 00:00:00 2001
From: Wonsuk Choi <sukvvon@gmail.com>
Date: Sun, 19 Jul 2026 02:20:20 +0900
Subject: [PATCH 2/2] test({react,preact}-query/usePrefetchQuery): drop the
 unnecessary 'vi.fn()' wrapper on the never-asserted sentinel queryFn

---
 packages/preact-query/src/__tests__/usePrefetchQuery.test.tsx | 2 +-
 packages/react-query/src/__tests__/usePrefetchQuery.test.tsx  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/preact-query/src/__tests__/usePrefetchQuery.test.tsx b/packages/preact-query/src/__tests__/usePrefetchQuery.test.tsx
index 725a5cfc2c..9dd5f3949d 100644
--- a/packages/preact-query/src/__tests__/usePrefetchQuery.test.tsx
+++ b/packages/preact-query/src/__tests__/usePrefetchQuery.test.tsx
@@ -37,7 +37,7 @@ describe('usePrefetchQuery', () => {
 
     const componentQueryOpts = {
       ...queryOpts,
-      queryFn: vi.fn(() => sleep(10).then(() => 'useSuspenseQuery')),
+      queryFn: () => sleep(10).then(() => 'useSuspenseQuery'),
     }
 
     function Page() {
diff --git a/packages/react-query/src/__tests__/usePrefetchQuery.test.tsx b/packages/react-query/src/__tests__/usePrefetchQuery.test.tsx
index 42bdb44e68..78dc11ad11 100644
--- a/packages/react-query/src/__tests__/usePrefetchQuery.test.tsx
+++ b/packages/react-query/src/__tests__/usePrefetchQuery.test.tsx
@@ -35,7 +35,7 @@ describe('usePrefetchQuery', () => {
 
     const componentQueryOpts = {
       ...queryOpts,
-      queryFn: vi.fn(() => sleep(10).then(() => 'useSuspenseQuery')),
+      queryFn: () => sleep(10).then(() => 'useSuspenseQuery'),
     }
 
     function Page() {