remove default timer mode, add flow types

export other timer helpers, adjust tests and docs

Author: mikeduminy

src/__tests__/timerUtils.js

@@ -1,27 +1,14 @@
-import { setTimeout } from '../helpers/getTimerFuncs';
+// @flow
+
+import { setTimeout } from '../helpers/timers';
 
 const TimerMode = {
-  Default: 'default',
   Legacy: 'legacy',
   Modern: 'modern', // broken for now
 };
 
-function setupFakeTimers(fakeTimerType) {
-  switch (fakeTimerType) {
-    case TimerMode.Legacy:
-    case TimerMode.Modern: {
-      jest.useFakeTimers(fakeTimerType);
-      break;
-    }
-    case TimerMode.Default:
-    default: {
-      jest.useFakeTimers();
-    }
-  }
-}
-
-async function sleep(ms) {
+async function sleep(ms: number): Promise<void> {
   return new Promise((resolve) => setTimeout(resolve, ms));
 }
 
-export { TimerMode, setupFakeTimers, sleep };
+export { TimerMode, sleep };

src/__tests__/timers.test.js

@@ -1,10 +1,12 @@
 import waitFor from '../waitFor';
-import { TimerMode, setupFakeTimers } from './timerUtils';
+import { TimerMode } from './timerUtils';
 
-describe.each([TimerMode.Default, TimerMode.Legacy])(
+describe.each([TimerMode.Legacy, TimerMode.Modern])(
   '%s fake timers tests',
   (fakeTimerType) => {
-    beforeEach(() => setupFakeTimers(fakeTimerType));
+    beforeEach(() => {
+      jest.useFakeTimers(fakeTimerType);
+    });
 
     test('it successfully runs tests', () => {
       expect(true).toBeTruthy();

src/__tests__/waitFor.test.js

@@ -2,7 +2,7 @@
 import * as React from 'react';
 import { Text, TouchableOpacity, View } from 'react-native';
 import { fireEvent, render, waitFor } from '..';
-import { TimerMode, setupFakeTimers, sleep } from './timerUtils';
+import { TimerMode } from './timerUtils';
 
 class Banana extends React.Component<any> {
   changeFresh = () => {
@@ -77,13 +77,13 @@ test('waits for element with custom interval', async () => {
     // suppress
   }
 
-  expect(mockFn).toHaveBeenCalledTimes(3);
+  expect(mockFn).toHaveBeenCalledTimes(2);
 });
 
-test.each([TimerMode.Default, TimerMode.Legacy])(
+test.each([TimerMode.Legacy, TimerMode.Modern])(
   'waits for element until it stops throwing using %s fake timers',
   async (fakeTimerType) => {
-    setupFakeTimers(fakeTimerType);
+    jest.useFakeTimers(fakeTimerType);
     const { getByText, queryByText } = render(<BananaContainer />);
 
     fireEvent.press(getByText('Change freshness!'));
@@ -96,10 +96,10 @@ test.each([TimerMode.Default, TimerMode.Legacy])(
   }
 );
 
-test.each([TimerMode.Default, TimerMode.Legacy])(
+test.each([TimerMode.Legacy, TimerMode.Modern])(
   'waits for assertion until timeout is met with %s fake timers',
   async (fakeTimerType) => {
-    setupFakeTimers(fakeTimerType);
+    jest.useFakeTimers(fakeTimerType);
 
     const mockFn = jest.fn(() => {
       throw Error('test');
@@ -115,10 +115,10 @@ test.each([TimerMode.Default, TimerMode.Legacy])(
   }
 );
 
-test.each([TimerMode.Default, TimerMode.Legacy])(
+test.each([TimerMode.Legacy, TimerMode.Legacy])(
   'awaiting something that succeeds before timeout works with %s fake timers',
   async (fakeTimerType) => {
-    setupFakeTimers(fakeTimerType);
+    jest.useFakeTimers(fakeTimerType);
 
     let calls = 0;
     const mockFn = jest.fn(() => {
@@ -137,30 +137,3 @@ test.each([TimerMode.Default, TimerMode.Legacy])(
     expect(mockFn).toHaveBeenCalledTimes(3);
   }
 );
-
-// this test leads to a console error: Warning: You called act(async () => ...) without await, but does not fail the test
-// it is included to show that the previous approach of faking modern timers still works
-// the gotcha is that the try catch will fail to catch the final error, which is why we need to stop throwing
-test('non-awaited approach is not affected by fake modern timers', async () => {
-  setupFakeTimers(TimerMode.Modern);
-
-  let calls = 0;
-  const mockFn = jest.fn(() => {
-    calls += 1;
-    if (calls < 3) {
-      throw Error('test');
-    }
-  });
-
-  try {
-    waitFor(() => mockFn(), { timeout: 400, interval: 200 });
-  } catch (e) {
-    // suppress
-  }
-  jest.advanceTimersByTime(400);
-  expect(mockFn).toHaveBeenCalledTimes(0);
-
-  jest.useRealTimers();
-  await sleep(500);
-  expect(mockFn).toHaveBeenCalledTimes(3);
-});

src/__tests__/waitForElementToBeRemoved.test.js

@@ -2,7 +2,7 @@
 import React, { useState } from 'react';
 import { View, Text, TouchableOpacity } from 'react-native';
 import { render, fireEvent, waitForElementToBeRemoved } from '..';
-import { TimerMode, setupFakeTimers } from './timerUtils';
+import { TimerMode } from './timerUtils';
 
 const TestSetup = ({ shouldUseDelay = true }) => {
   const [isAdded, setIsAdded] = useState(true);
@@ -121,7 +121,7 @@ test('waits with custom interval', async () => {
 
   try {
     await waitForElementToBeRemoved(() => mockFn(), {
-      timeout: 400,
+      timeout: 600,
       interval: 200,
     });
   } catch (e) {
@@ -131,10 +131,10 @@ test('waits with custom interval', async () => {
   expect(mockFn).toHaveBeenCalledTimes(4);
 });
 
-test.each([TimerMode.Default, TimerMode.Legacy])(
+test.each([TimerMode.Legacy, TimerMode.Modern])(
   'works with %s fake timers',
   async (fakeTimerType) => {
-    setupFakeTimers(fakeTimerType);
+    jest.useFakeTimers(fakeTimerType);
 
     const mockFn = jest.fn(() => <View />);
 
@@ -146,6 +146,6 @@ test.each([TimerMode.Default, TimerMode.Legacy])(
     } catch (e) {
       // Suppress expected error
     }
-    expect(mockFn).toHaveBeenCalledTimes(4);
+    expect(mockFn).toHaveBeenCalledTimes(2);
   }
 );

src/flushMicroTasks.js

@@ -1,6 +1,6 @@
 // @flow
 import { printDeprecationWarning } from './helpers/errors';
-import { setImmediate } from './helpers/getTimerFuncs';
+import { setImmediate } from './helpers/timers';
 
 type Thenable<T> = { then: (() => T) => mixed };
 

src/helpers/getTimerFuncs.js renamed to src/helpers/timers.js

@@ -1,11 +1,11 @@
-/* eslint-disable no-undef */
-
-// Contents of this file sourced directly from https://github.com/testing-library/dom-testing-library/blob/master/src/helpers.js
+// Most content of this file sourced directly from https://github.com/testing-library/dom-testing-library/blob/master/src/helpers.js
+// @flow
+/* globals jest */
 
 const globalObj = typeof window === 'undefined' ? global : window;
 
 // Currently this fn only supports jest timers, but it could support other test runners in the future.
-function runWithRealTimers(callback) {
+function runWithRealTimers<T>(callback: () => T): T {
   const fakeTimersType = getJestFakeTimersType();
   if (fakeTimersType) {
     jest.useRealTimers();
@@ -21,6 +21,7 @@ function runWithRealTimers(callback) {
 }
 
 function getJestFakeTimersType() {
+  // istanbul ignore if
   if (
     typeof jest === 'undefined' ||
     typeof globalObj.setTimeout === 'undefined'
@@ -37,10 +38,12 @@ function getJestFakeTimersType() {
 
   if (
     typeof globalObj.setTimeout.clock !== 'undefined' &&
+    // $FlowIgnore[prop-missing]
     typeof jest.getRealSystemTime !== 'undefined'
   ) {
     try {
       // jest.getRealSystemTime is only supported for Jest's `modern` fake timers and otherwise throws
+      // $FlowExpectedError
       jest.getRealSystemTime();
       return 'modern';
     } catch {
@@ -50,24 +53,35 @@ function getJestFakeTimersType() {
   return null;
 }
 
+const jestFakeTimersAreEnabled = (): boolean =>
+  Boolean(getJestFakeTimersType());
+
 // we only run our tests in node, and setImmediate is supported in node.
 function setImmediatePolyfill(fn) {
   return globalObj.setTimeout(fn, 0);
 }
 
-function getTimeFunctions() {
+type BindTimeFunctions = {
+  clearTimeoutFn: typeof clearTimeout,
+  setImmediateFn: typeof setImmediate,
+  setTimeoutFn: typeof setTimeout,
+};
+
+function bindTimeFunctions(): BindTimeFunctions {
   return {
     clearTimeoutFn: globalObj.clearTimeout,
     setImmediateFn: globalObj.setImmediate || setImmediatePolyfill,
     setTimeoutFn: globalObj.setTimeout,
   };
 }
 
-const { clearTimeoutFn, setImmediateFn, setTimeoutFn } = runWithRealTimers(
-  getTimeFunctions
-);
+const { clearTimeoutFn, setImmediateFn, setTimeoutFn } = (runWithRealTimers(
+  bindTimeFunctions
+): BindTimeFunctions);
 
 export {
+  runWithRealTimers,
+  jestFakeTimersAreEnabled,
   clearTimeoutFn as clearTimeout,
   setImmediateFn as setImmediate,
   setTimeoutFn as setTimeout,

website/docs/API.md

@@ -366,8 +366,6 @@ test('waiting for an Banana to be ready', async () => {
 In order to properly use `waitFor` you need at least React >=16.9.0 (featuring async `act`) or React Native >=0.60 (which comes with React >=16.9.0).
 :::
 
-If you're using Jest's [Timer Mocks](https://jestjs.io/docs/en/timer-mocks#docsNav), remember not to await the return of `waitFor` as it will stall your tests.
-
 ## `waitForElementToBeRemoved`
 
 - [`Example code`](https://github.com/callstack/react-native-testing-library/blob/master/src/__tests__/waitForElementToBeRemoved.test.js)
@@ -404,8 +402,6 @@ You can use any of `getBy`, `getAllBy`, `queryBy` and `queryAllBy` queries for `
 In order to properly use `waitForElementToBeRemoved` you need at least React >=16.9.0 (featuring async `act`) or React Native >=0.60 (which comes with React >=16.9.0).
 :::
 
-If you're using Jest's [Timer Mocks](https://jestjs.io/docs/en/timer-mocks#docsNav), remember not to await the return of `waitFor` as it will stall your tests.
-
 ## `within`, `getQueriesForElement`
 
 - [`Example code`](https://github.com/callstack/react-native-testing-library/blob/master/src/__tests__/within.test.js)