Ignore fake timers

src/helpers/__tests__/timers.test.ts

@@ -0,0 +1,8 @@
+import { jestFakeTimersAreEnabled } from '../timers';
+describe('timers', () => {
+  it('should not mock timers if RNTL_SKIP_AUTO_DETECT_FAKE_TIMERS is set', async () => {
+    process.env.RNTL_SKIP_AUTO_DETECT_FAKE_TIMERS = 'true';
+    jest.useFakeTimers();
+    expect(jestFakeTimersAreEnabled()).toEqual(false);
+  });
+});

src/helpers/timers.ts

@@ -25,7 +25,8 @@ function getJestFakeTimersType(): FakeTimersTypes | null {
   // istanbul ignore if
   if (
     typeof jest === 'undefined' ||
-    typeof globalObj.setTimeout === 'undefined'
+    typeof globalObj.setTimeout === 'undefined' ||
+    process.env.RNTL_SKIP_AUTO_DETECT_FAKE_TIMERS
   ) {
     return null;
   }

website/docs/API.md

@@ -49,6 +49,9 @@ title: API
   - [`configure`](#configure)
     - [`asyncUtilTimeout` option](#asyncutiltimeout-option)
   - [`resetToDefaults()`](#resettodefaults)
+  - [Environment variables](#environment-variables)
+    - [`RNTL_SKIP_AUTO_CLEANUP`](#rntl_skip_auto_cleanup)
+    - [`RNTL_SKIP_AUTO_DETECT_FAKE_TIMERS`](#rntl_skip_auto_detect_fake_timers)
 - [Accessibility](#accessibility)
   - [`isInaccessible`](#isinaccessible)
 
@@ -730,7 +733,6 @@ type Config = {
 
 function configure(options: Partial<Config>)  {}
 ```
-
 #### `asyncUtilTimeout` option
 
 Default timeout, in ms, for async helper functions (`waitFor`, `waitForElementToBeRemoved`) and `findBy*` queries. Defaults to 1000 ms.
@@ -742,6 +744,22 @@ Default timeout, in ms, for async helper functions (`waitFor`, `waitForElementTo
 function resetToDefaults() {}
 ```
 
+### Environment variables
+
+#### `RNTL_SKIP_AUTO_CLEANUP`
+Set to `true` to disable automatic `cleanup()` after each test. It works the same as importing `react-native-testing-library/dont-cleanup-after-each` or using `react-native-testing-library/pure`.
+
+```shell
+$ RNTL_SKIP_AUTO_CLEANUP=true jest
+```
+
+#### `RNTL_SKIP_AUTO_DETECT_FAKE_TIMERS`
+Set to `true` to disable auto-detection of fake timers. This might be useful in rare cases when you want to use non-Jest fake timers. See [issue #886](https://github.com/callstack/react-native-testing-library/issues/886) for more details.
+
+```shell
+$ RNTL_SKIP_AUTO_DETECT_FAKE_TIMERS=true jest
+```
+
 ## Accessibility
 
 ### `isInaccessible`

website/docs/MigrationV2.md

@@ -26,7 +26,7 @@ This change might break your code, if you tests are not isolated, i.e. you call
   }
   ```
 
-- by setting `RTNL_SKIP_AUTO_CLEANUP` env variable to `true`. You can do this with `cross-evn` like this:
+- by setting `RNTL_SKIP_AUTO_CLEANUP` env variable to `true`. You can do this with `cross-evn` like this:
 
   ```sh
   cross-env RNTL_SKIP_AUTO_CLEANUP=true jest