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Author: Sebastian Silbermann

src/__tests__/__snapshots__/waitFor.test.js.snap

@@ -0,0 +1,7 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`waitFor DOM reference implementation using fake legacy timers timeout 1`] = `Not done`;
+
+exports[`waitFor DOM reference implementation using fake modern timers timeout 1`] = `Not done`;
+
+exports[`waitFor DOM reference implementation using real timers timeout 1`] = `Not done`;

src/__tests__/waitFor.test.js

@@ -131,13 +131,25 @@ test('does not work after it resolves', async () => {
     // @testing-library/react usage to ensure `IS_REACT_ACT_ENVIRONMENT` is set when acting.
     advanceTimersByTime: async timeoutMS => {
       const originalContext = context
-      context = 'no-act'
+      context = 'act'
       try {
         jest.advanceTimersByTime(timeoutMS)
       } finally {
         context = originalContext
       }
     },
+    flushPromises: async () => {
+      const originalContext = context
+      context = 'no-act'
+      try {
+        await await new Promise(r => {
+          setTimeout(r, 0)
+          jest.advanceTimersByTime(0)
+        })
+      } finally {
+        context = originalContext
+      }
+    },
   }
 
   let data = null
@@ -161,3 +173,75 @@ test('does not work after it resolves', async () => {
 
   expect(context).toEqual('initial')
 })
+
+/** @type {import('../').FakeClock} */
+const jestFakeClock = {
+  advanceTimersByTime: timeoutMS => {
+    jest.advanceTimersByTime(timeoutMS)
+  },
+  flushPromises: () => {
+    return new Promise(r => {
+      setTimeout(r, 0)
+      jest.advanceTimersByTime(0)
+    })
+  },
+}
+describe.each([
+  ['real timers', {useTimers: () => jest.useRealTimers(), clock: undefined}],
+  [
+    'fake legacy timers',
+    {useTimers: () => jest.useFakeTimers('legacy'), clock: jestFakeClock},
+  ],
+  [
+    'fake modern timers',
+    {useTimers: () => jest.useFakeTimers('modern'), clock: jestFakeClock},
+  ],
+])(
+  'waitFor DOM reference implementation using %s',
+  (label, {useTimers, clock}) => {
+    beforeEach(() => {
+      useTimers()
+    })
+
+    afterEach(() => {
+      jest.useRealTimers()
+    })
+
+    test('void callback', async () => {
+      await expect(waitFor(() => {}, {clock})).resolves.toBeUndefined()
+    })
+
+    test('callback passes after timeout', async () => {
+      let state = 'pending'
+      setTimeout(() => {
+        state = 'done'
+      }, 10)
+
+      await expect(
+        waitFor(
+          () => {
+            if (state !== 'done') {
+              throw new Error('Not done')
+            }
+          },
+          {clock, interval: 5},
+        ),
+      ).resolves.toBeUndefined()
+    })
+
+    test('timeout', async () => {
+      const state = 'pending'
+
+      await expect(
+        waitFor(
+          () => {
+            if (state !== 'done') {
+              throw new Error('Not done')
+            }
+          },
+          {clock, timeout: 10},
+        ),
+      ).rejects.toThrowErrorMatchingSnapshot()
+    })
+  },
+)