chore: more tests (#1857)

Author: mdjastrzebski

src/__tests__/act.test.tsx

@@ -2,6 +2,7 @@ import * as React from 'react';
 import { Text } from 'react-native';
 
 import { act, fireEvent, render, screen } from '..';
+import { getIsReactActEnvironment } from '../act';
 
 type UseEffectProps = { callback(): void };
 const UseEffect = ({ callback }: UseEffectProps) => {
@@ -48,3 +49,32 @@ test('should be able to await act', async () => {
 test('should be able to await act when promise rejects', async () => {
   await expect(act(() => Promise.reject('error'))).rejects.toBe('error');
 });
+
+test('should restore act environment when callback throws synchronously', async () => {
+  const previousEnvironment = getIsReactActEnvironment();
+
+  const testError = new Error('Synchronous error in act');
+
+  await expect(
+    act(() => {
+      throw testError;
+    }),
+  ).rejects.toBe(testError);
+
+  // Verify the act environment was restored even after error
+  expect(getIsReactActEnvironment()).toBe(previousEnvironment);
+});
+
+test('should restore act environment when callback returns non-promise value', async () => {
+  const previousEnvironment = getIsReactActEnvironment();
+
+  // Call act with a callback that returns a non-promise value
+  // This tests the else branch in withGlobalActEnvironment
+  const result = await act(() => {
+    return 42;
+  });
+
+  expect(result).toBe(42);
+  // Verify the act environment was restored
+  expect(getIsReactActEnvironment()).toBe(previousEnvironment);
+});

src/__tests__/wait-for.test.tsx

@@ -316,3 +316,34 @@ test('waitFor throws if expectation is not a function', async () => {
     waitFor('not a function'),
   ).rejects.toThrowErrorMatchingInlineSnapshot(`"Received \`expectation\` arg must be a function"`);
 });
+
+test.each([false, true])(
+  'waitFor throws clear error when switching from fake timers to real timers (legacyFakeTimers = %s)',
+  async (legacyFakeTimers) => {
+    jest.useFakeTimers({ legacyFakeTimers });
+
+    const waitForPromise = waitFor(() => {
+      // Switch to real timers during waitFor - this should trigger an error
+      jest.useRealTimers();
+      throw new Error('test');
+    });
+
+    await expect(waitForPromise).rejects.toThrow(
+      'Changed from using fake timers to real timers while using waitFor',
+    );
+  },
+);
+
+test('waitFor throws clear error when switching from real timers to fake timers', async () => {
+  jest.useRealTimers();
+
+  const waitForPromise = waitFor(() => {
+    // Switch to fake timers during waitFor - this should trigger an error
+    jest.useFakeTimers();
+    throw new Error('test');
+  });
+
+  await expect(waitForPromise).rejects.toThrow(
+    'Changed from using real timers to fake timers while using waitFor',
+  );
+});