jestjs · SimenB · Apr 5, 2022 · Mar 12, 2022 · Mar 12, 2022 · Mar 12, 2022
diff --git a/e2e/__tests__/__snapshots__/showConfig.test.ts.snap b/e2e/__tests__/__snapshots__/showConfig.test.ts.snap
@@ -66,7 +66,9 @@ exports[`--showConfig outputs config info and exits 1`] = `
       ],
       "testRegex": [],
       "testRunner": "<<REPLACED_JEST_PACKAGES_DIR>>/jest-circus/runner.js",
-      "timers": "real",
+      "timers": {
+        "loopLimit": 100000
+      },
       "transform": [
         [
           "\\\\.[jt]sx?$",

diff --git a/e2e/fake-promises/asap/package.json b/e2e/fake-promises/asap/package.json
@@ -1,9 +1,9 @@
 {
   "jest": {
-    "timers": "fake",
     "setupFiles": [
       "<rootDir>/fake-promises"
     ],
-    "testEnvironment": "node"
+    "testEnvironment": "node",
+    "timers": {"strategy": "modern"}
   }
 }
diff --git a/e2e/fake-promises/immediate/package.json b/e2e/fake-promises/immediate/package.json
@@ -1,9 +1,9 @@
 {
   "jest": {
-    "timers": "fake",
     "setupFiles": [
       "<rootDir>/fake-promises"
     ],
-    "testEnvironment": "node"
+    "testEnvironment": "node",
+    "timers": {"strategy": "modern"}
   }
 }
diff --git a/e2e/fake-time/legacy/from-config/package.json b/e2e/fake-time/legacy/from-config/package.json
@@ -1,6 +1,6 @@
 {
   "jest": {
-    "timers": "legacy",
-    "testEnvironment": "node"
+    "testEnvironment": "node",
+    "timers": {"strategy": "legacy"}
   }
 }
diff --git a/e2e/fake-time/legacy/from-jest-object/__tests__/test.js b/e2e/fake-time/legacy/from-jest-object/__tests__/test.js
@@ -8,7 +8,7 @@
 'use strict';
 
 test('fake timers', () => {
-  jest.useFakeTimers('legacy');
+  jest.useFakeTimers({strategy: 'legacy'});
 
   expect(() => jest.setSystemTime(0)).toThrow(
     'setSystemTime is not available when not using modern timers',

diff --git a/e2e/fake-time/legacy/requestAnimationFrame/__tests__/test.js b/e2e/fake-time/legacy/requestAnimationFrame/__tests__/test.js
@@ -10,7 +10,7 @@
 'use strict';
 
 test('requestAnimationFrame', () => {
-  jest.useFakeTimers('legacy');
+  jest.useFakeTimers({strategy: 'legacy'});
   let frameTimestamp = -1;
   requestAnimationFrame(timestamp => {
     frameTimestamp = timestamp;

diff --git a/e2e/fake-time/modern/from-config/package.json b/e2e/fake-time/modern/from-config/package.json
@@ -1,6 +1,6 @@
 {
   "jest": {
-    "timers": "fake",
-    "testEnvironment": "node"
+    "testEnvironment": "node",
+    "timers": {"strategy": "modern"}
   }
 }
diff --git a/e2e/fake-time/modern/requestAnimationFrame/__tests__/test.js b/e2e/fake-time/modern/requestAnimationFrame/__tests__/test.js
@@ -10,7 +10,8 @@
 'use strict';
 
 test('requestAnimationFrame', () => {
-  jest.useFakeTimers('modern');
+  jest.useFakeTimers();
+
   let frameTimestamp = -1;
   requestAnimationFrame(timestamp => {
     frameTimestamp = timestamp;

diff --git a/e2e/modern-fake-timers/from-config/package.json b/e2e/modern-fake-timers/from-config/package.json
@@ -1,6 +1,6 @@
 {
   "jest": {
-    "timers": "modern",
-    "testEnvironment": "node"
+    "testEnvironment": "node",
+    "timers": {"strategy": "modern"}
   }
 }
diff --git a/e2e/modern-fake-timers/from-jest-object/__tests__/test.js b/e2e/modern-fake-timers/from-jest-object/__tests__/test.js
@@ -8,7 +8,7 @@
 'use strict';
 
 test('fake timers with number argument', () => {
-  jest.useFakeTimers('modern');
+  jest.useFakeTimers();
 
   jest.setSystemTime(0);
 
@@ -20,7 +20,7 @@ test('fake timers with number argument', () => {
 });
 
 test('fake timers with Date argument', () => {
-  jest.useFakeTimers('modern');
+  jest.useFakeTimers();
 
   jest.setSystemTime(new Date(0));
 

diff --git a/e2e/set-immediate/package.json b/e2e/set-immediate/package.json
@@ -1,6 +1,6 @@
 {
   "jest": {
     "testEnvironment": "node",
-    "timers": "fake"
+    "timers": {"strategy": "modern"}
   }
 }
diff --git a/e2e/timer-reset-mocks/with-reset-mocks/package.json b/e2e/timer-reset-mocks/with-reset-mocks/package.json
@@ -1,7 +1,7 @@
 {
   "jest": {
-    "testEnvironment": "node",
     "resetMocks": true,
-    "timers": "fake"
+    "testEnvironment": "node",
+    "timers": {"strategy": "modern"}
   }
 }
diff --git a/e2e/timer-use-real-timers/package.json b/e2e/timer-use-real-timers/package.json
@@ -1,6 +1,6 @@
 {
   "jest": {
     "testEnvironment": "node",
-    "timers": "fake"
+    "timers": {"strategy": "modern"}
   }
 }
diff --git a/packages/jest-circus/src/legacy-code-todo-rewrite/jestAdapter.ts b/packages/jest-circus/src/legacy-code-todo-rewrite/jestAdapter.ts
@@ -38,10 +38,10 @@ const jestAdapter = async (
     testPath,
   });
 
-  if (config.timers === 'fake' || config.timers === 'modern') {
+  if (config.timers.strategy === 'modern') {
     // during setup, this cannot be null (and it's fine to explode if it is)
-    environment.fakeTimersModern!.useFakeTimers();
-  } else if (config.timers === 'legacy') {
+    environment.fakeTimersModern!.useFakeTimers(config.timers);
+  } else if (config.timers.strategy === 'legacy') {
     environment.fakeTimers!.useFakeTimers();
   }
 

diff --git a/packages/jest-cli/src/init/__tests__/__snapshots__/init.test.js.snap b/packages/jest-cli/src/init/__tests__/__snapshots__/init.test.js.snap
@@ -284,7 +284,9 @@ module.exports = {
   // testRunner: "jest-circus/runner",
 
   // Setting this value to "fake" allows the use of fake timers for functions such as "setTimeout"
-  // timers: "real",
+  // timers: {
+  //   "loopLimit": 100000
+  // },
 
   // A map from regular expressions to paths to transformers
   // transform: undefined,

diff --git a/packages/jest-config/src/Defaults.ts b/packages/jest-config/src/Defaults.ts
@@ -72,7 +72,7 @@ const defaultOptions: Config.DefaultOptions = {
   testRegex: [],
   testRunner: 'jest-circus/runner',
   testSequencer: '@jest/test-sequencer',
-  timers: 'real',
+  timers: {loopLimit: 100_000},
   transformIgnorePatterns: [NODE_MODULES_REGEXP, `\\.pnp\\.[^\\${sep}]+$`],
   useStderr: false,
   watch: false,

diff --git a/packages/jest-config/src/Descriptions.ts b/packages/jest-config/src/Descriptions.ts
@@ -84,6 +84,7 @@ const descriptions: {[key in keyof Config.InitialOptions]: string} = {
   testResultsProcessor:
     'This option allows the use of a custom results processor',
   testRunner: 'This option allows use of a custom test runner',
+  // TODO
   timers:
     'Setting this value to "fake" allows the use of fake timers for functions such as "setTimeout"',
   transform: 'A map from regular expressions to paths to transformers',

diff --git a/packages/jest-config/src/ValidConfig.ts b/packages/jest-config/src/ValidConfig.ts
@@ -132,7 +132,34 @@ const initialOptions: Config.InitialOptions = {
   testRunner: 'circus',
   testSequencer: '@jest/test-sequencer',
   testTimeout: 5000,
-  timers: 'real',
+  timers: multipleValidOptions(
+    {loopLimit: 1000, strategy: 'legacy'} as const,
+    {
+      advanceTimeDelta: 1000,
+      loopLimit: 1000,
+      now: multipleValidOptions(0, new Date()),
+      shouldAdvanceTime: false,
+      shouldClearNativeTimers: false,
+      strategy: 'modern',
+      toFake: [
+        'setImmediate',
+        'clearImmediate',
+        'setInterval',
+        'clearInterval',
+        'setTimeout',
+        'clearTimeout',
+        'requestAnimationFrame',
+        'cancelAnimationFrame',
+        'requestIdleCallback',
+        'cancelIdleCallback',
+        'Date',
+        'hrtime',
+        'nextTick',
+        'performance',
+        'queueMicrotask', // ?
+      ] as Array<Config.FakeableTimerAPIs>,
+    } as const,
+  ),
   transform: {
     '\\.js$': '<rootDir>/preprocessor.js',
   },

diff --git a/packages/jest-core/src/lib/__tests__/__snapshots__/logDebugMessages.test.ts.snap b/packages/jest-core/src/lib/__tests__/__snapshots__/logDebugMessages.test.ts.snap
@@ -52,7 +52,9 @@ exports[`prints the config object 1`] = `
       "\\\\.test\\\\.js$"
     ],
     "testRunner": "myRunner",
-    "timers": "real",
+    "timers": {
+      "loopLimit": 100000
+    },
     "transform": [],
     "transformIgnorePatterns": [],
     "watchPathIgnorePatterns": []

diff --git a/packages/jest-environment/src/index.ts b/packages/jest-environment/src/index.ts
@@ -304,7 +304,7 @@ export interface Jest {
   /**
    * Instructs Jest to use fake versions of the standard timer functions.
    */
-  useFakeTimers(implementation?: 'modern' | 'legacy'): Jest;
+  useFakeTimers(timersConfig?: Config.TimersConfig): Jest;
   /**
    * Instructs Jest to use the real versions of the standard timer functions.
    */

diff --git a/packages/jest-fake-timers/package.json b/packages/jest-fake-timers/package.json
@@ -25,6 +25,7 @@
     "jest-util": "^28.0.0-alpha.7"
   },
   "devDependencies": {
+    "@jest/test-utils": "^28.0.0-alpha.7",
     "@types/sinonjs__fake-timers": "^8.1.1"
   },
   "engines": {

diff --git a/packages/jest-fake-timers/src/__tests__/__snapshots__/modernFakeTimers.test.ts.snap b/packages/jest-fake-timers/src/__tests__/__snapshots__/modernFakeTimers.test.ts.snap
@@ -1,3 +1,3 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`FakeTimers runAllTimers warns when trying to advance timers while real timers are used 1`] = `"A function to advance timers was called but the timers API is not mocked with fake timers. Call \`jest.useFakeTimers()\` in this test or enable fake timers globally by setting \`"timers": "fake"\` in the configuration file"`;
+exports[`FakeTimers runAllTimers warns when trying to advance timers while real timers are used 1`] = `"A function to advance timers was called but the timers API is not mocked with fake timers. Call \`jest.useFakeTimers()\` in this test or enable fake timers globally using "timers" option in the Jest configuration file"`;