Exposes globalConfig to custom test sequencers (#14535)

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### Features
 
+- `[jest-test-sequencer, jest-core]` Exposes globalConfig & contexts to TestSequencer ([#14535](https://github.com/jestjs/jest/pull/14535))
+
 ### Fixes
 
 - `[jest-leak-detector]` Make leak-detector more aggressive when running GC ([#14526](https://github.com/jestjs/jest/pull/14526))

e2e/__tests__/customTestSequencers.test.ts

@@ -79,3 +79,55 @@ test('run failed tests async', () => {
     .split('\n');
   expect(sequence).toEqual(['./c.test.js', './d.test.js']);
 });
+
+test('run tests based on even seed', () => {
+  const result = runJest(
+    dir,
+    [
+      '-i',
+      '--config',
+      JSON.stringify({
+        testSequencer: '<rootDir>/testSequencerWithSeed.js',
+      }),
+      '--seed=2',
+    ],
+    {},
+  );
+  expect(result.exitCode).toBe(0);
+  const sequence = extractSummary(result.stderr)
+    .rest.replace(/PASS /g, '')
+    .split('\n');
+  expect(sequence).toEqual([
+    './a.test.js',
+    './b.test.js',
+    './c.test.js',
+    './d.test.js',
+    './e.test.js',
+  ]);
+});
+
+test('run tests based on odd seed', () => {
+  const result = runJest(
+    dir,
+    [
+      '-i',
+      '--config',
+      JSON.stringify({
+        testSequencer: '<rootDir>/testSequencerWithSeed.js',
+      }),
+      '--seed=1',
+    ],
+    {},
+  );
+  expect(result.exitCode).toBe(0);
+  const sequence = extractSummary(result.stderr)
+    .rest.replace(/PASS /g, '')
+    .split('\n');
+  expect(sequence).toEqual([
+    './e.test.js',
+    './d.test.js',
+    './c.test.js',
+    './b.test.js',
+    './a.test.js',
+  ]);
+});

e2e/custom-test-sequencer/testSequencerWithSeed.js

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+const Sequencer = require('@jest/test-sequencer').default;
+
+class CustomSequencer extends Sequencer {
+  constructor(_options) {
+    super(_options);
+    this.globalConfig = _options.globalConfig;
+  }
+
+  sort(tests) {
+    const copyTests = Array.from(tests);
+    const seed = this.globalConfig.seed;
+    const sortedTests = copyTests.sort((testA, testB) =>
+      testA.path > testB.path ? 1 : -1,
+    );
+
+    if (seed % 2 === 0) {
+      return sortedTests;
+    } else {
+      return sortedTests.reverse();
+    }
+  }
+}
+
+module.exports = CustomSequencer;

packages/jest-core/src/runJest.ts

@@ -159,7 +159,7 @@ export default async function runJest({
   const Sequencer: typeof TestSequencer = await requireOrImportModule(
     globalConfig.testSequencer,
   );
-  const sequencer = new Sequencer();
+  const sequencer = new Sequencer({contexts, globalConfig});
   let allTests: Array<Test> = [];
 
   if (changedFilesPromise && globalConfig.watch) {

packages/jest-test-sequencer/src/index.ts

@@ -10,11 +10,17 @@ import * as path from 'path';
 import * as fs from 'graceful-fs';
 import slash = require('slash');
 import type {AggregatedResult, Test, TestContext} from '@jest/test-result';
+import type {Config} from '@jest/types';
 import HasteMap from 'jest-haste-map';
 
 const FAIL = 0;
 const SUCCESS = 1;
 
+export type TestSequencerOptions = {
+  contexts: ReadonlyArray<TestContext>;
+  globalConfig: Config.GlobalConfig;
+};
+
 type Cache = {
   [key: string]:
     | [testStatus: typeof FAIL | typeof SUCCESS, testDuration: number]
@@ -46,6 +52,9 @@ type ShardPositionOptions = ShardOptions & {
 export default class TestSequencer {
   private readonly _cache = new Map<TestContext, Cache>();
 
+  // eslint-disable-next-line @typescript-eslint/no-empty-function
+  constructor(_options?: TestSequencerOptions) {}
+
   _getCachePath(testContext: TestContext): string {
     const {config} = testContext;
     const HasteMapClass = HasteMap.getStatic(config);