fix(jest-runner): allow a different rootDir

The Jest Runner now adhers to the way Jest deremines the [rootDir](https://jestjs.io/docs/configuration#rootdir-string).

e2e/test/coverage-analysis/jest-spec/jest.config.json

@@ -1,4 +1,5 @@
 {
   "testEnvironment": "node",
-  "testMatch": ["**/jest-spec/*.spec.js"]
+  "rootDir": "..",
+  "testMatch": ["<rootDir>/jest-spec/*.spec.js"]
 }

packages/jest-runner/src/config-loaders/custom-jest-config-loader.ts

@@ -51,7 +51,7 @@ export class CustomJestConfigLoader implements JestConfigLoader {
   private resolvePackageJsonFilePath(): string | undefined {
     const jestOptions = this.options as JestRunnerOptionsWithStrykerOptions;
     const packageJsonCandidate = path.resolve(jestOptions.jest.configFile ?? 'package.json');
-    if (packageJsonCandidate.endsWith('.json') && (jestOptions.jest.configFile || fs.existsSync(packageJsonCandidate))) {
+    if (packageJsonCandidate.endsWith('package.json') && (jestOptions.jest.configFile || fs.existsSync(packageJsonCandidate))) {
       return packageJsonCandidate;
     }
     return undefined;
@@ -63,7 +63,7 @@ export class CustomJestConfigLoader implements JestConfigLoader {
   private resolveJestConfigFilePath(): string | undefined {
     const jestOptions = this.options as JestRunnerOptionsWithStrykerOptions;
     const configFileCandidate = path.resolve(jestOptions.jest.configFile ?? 'jest.config.js');
-    if (configFileCandidate.endsWith('.js') && (jestOptions.jest.configFile || fs.existsSync(configFileCandidate))) {
+    if (!configFileCandidate.endsWith('package.json') && (jestOptions.jest.configFile || fs.existsSync(configFileCandidate))) {
       return configFileCandidate;
     }
     return undefined;

packages/jest-runner/src/jest-test-adapters/jest-greater-than-25-adapter.ts

@@ -4,7 +4,7 @@ import { JestRunResult } from '../jest-run-result';
 import { JestTestAdapter, RunSettings } from './jest-test-adapter';
 
 export class JestGreaterThan25TestAdapter implements JestTestAdapter {
-  public async run({ jestConfig, projectRoot, fileNameUnderTest, testNamePattern, testLocationInResults }: RunSettings): Promise<JestRunResult> {
+  public async run({ jestConfig, fileNameUnderTest, testNamePattern, testLocationInResults }: RunSettings): Promise<JestRunResult> {
     const config = JSON.stringify(jestConfig);
     const result = await jestWrapper.runCLI(
       {
@@ -17,7 +17,7 @@ export class JestGreaterThan25TestAdapter implements JestTestAdapter {
         testNamePattern,
         testLocationInResults,
       },
-      [projectRoot]
+      [jestConfig.rootDir ?? process.cwd()]
     );
     return result;
   }

packages/jest-runner/src/jest-test-adapters/jest-less-than-25-adapter.ts

@@ -1,5 +1,3 @@
-import { Config } from '@jest/types';
-
 import { jestWrapper } from '../utils';
 import { JestRunResult } from '../jest-run-result';
 
@@ -10,17 +8,20 @@ import { RunSettings, JestTestAdapter } from './jest-test-adapter';
  * It has a lot of `any` typings here, since the installed typings are not in sync.
  */
 export class JestLessThan25TestAdapter implements JestTestAdapter {
-  public run({ jestConfig, projectRoot, fileNameUnderTest, testNamePattern, testLocationInResults }: RunSettings): Promise<JestRunResult> {
+  public run({ jestConfig, fileNameUnderTest, testNamePattern, testLocationInResults }: RunSettings): Promise<JestRunResult> {
     const config = JSON.stringify(jestConfig);
     return jestWrapper.runCLI(
       {
-        ...(fileNameUnderTest && { _: [fileNameUnderTest], findRelatedTests: true }),
+        $0: 'stryker',
+        _: fileNameUnderTest ? [fileNameUnderTest] : [],
+        findRelatedTests: !!fileNameUnderTest,
         config,
         runInBand: true,
         silent: true,
         testNamePattern,
-      } as Config.Argv,
-      [projectRoot]
+        testLocationInResults,
+      },
+      [jestConfig.rootDir ?? process.cwd()]
     );
   }
 }

packages/jest-runner/src/jest-test-adapters/jest-test-adapter.ts

@@ -4,7 +4,6 @@ import { JestRunResult } from '../jest-run-result';
 
 export interface RunSettings {
   jestConfig: Config.InitialOptions;
-  projectRoot: string;
   testNamePattern?: string;
   fileNameUnderTest?: string;
   testLocationInResults?: boolean;

packages/jest-runner/src/jest-test-runner.ts

@@ -106,7 +106,6 @@ export class JestTestRunner implements TestRunner {
     try {
       const { dryRunResult, jestResult } = await this.run({
         jestConfig: withCoverageAnalysis(this.jestConfig, coverageAnalysis),
-        projectRoot: process.cwd(),
         testLocationInResults: true,
       });
       if (dryRunResult.status === DryRunStatus.Complete && coverageAnalysis !== 'off') {
@@ -138,7 +137,6 @@ export class JestTestRunner implements TestRunner {
       const { dryRunResult } = await this.run({
         fileNameUnderTest,
         jestConfig: this.configForMutantRun(fileNameUnderTest),
-        projectRoot: process.cwd(),
         testNamePattern,
       });
       return toMutantRunResult(dryRunResult);

packages/jest-runner/src/plugin-tokens.ts

@@ -1,5 +1,3 @@
-export const projectRoot = 'projectRoot';
-export const loader = 'loader';
 export const resolve = 'resolve';
 export const configLoader = 'configLoader';
 export const processEnv = 'processEnv';

packages/jest-runner/src/utils/index.ts

@@ -1,4 +1,3 @@
-export * from './create-react-jest-config';
 export * from './verify-all-test-files-have-coverage';
 export * from './merge-mutant-coverage';
 export * from './jest-wrapper';

packages/jest-runner/test/integration/config-in-child-dir.it.spec.ts

@@ -0,0 +1,27 @@
+import { commonTokens } from '@stryker-mutator/api/plugin';
+import { assertions, factory, testInjector } from '@stryker-mutator/test-helpers';
+import { expect } from 'chai';
+
+import { JestOptions } from '../../src-generated/jest-runner-options';
+import { JestRunnerOptionsWithStrykerOptions } from '../../src/jest-runner-options-with-stryker-options';
+import { jestTestRunnerFactory } from '../../src/jest-test-runner';
+import { createJestOptions } from '../helpers/producers';
+
+import { resolveTestResource } from '../helpers/resolve-test-resource';
+
+describe('jest with config in child dir', () => {
+  function createSut(overrides?: Partial<JestOptions>) {
+    const options: JestRunnerOptionsWithStrykerOptions = factory.strykerWithPluginOptions({
+      jest: createJestOptions(overrides),
+    });
+    return testInjector.injector.provideValue(commonTokens.options, options).injectFunction(jestTestRunnerFactory);
+  }
+
+  it('should still be able perform a mutant run', async () => {
+    process.chdir(resolveTestResource('config-in-child-dir'));
+    const sut = createSut({ configFile: 'client/jest.config.js' });
+    const actual = await sut.dryRun(factory.dryRunOptions());
+    assertions.expectCompleted(actual);
+    expect(actual.tests).lengthOf(2);
+  });
+});

packages/jest-runner/test/unit/config-loaders/custom-config-loader.spec.ts

@@ -57,6 +57,19 @@ describe(CustomJestConfigLoader.name, () => {
     expect(config).to.deep.contains({ rootDir: path.resolve(projectRoot, 'lib') });
   });
 
+  it('should allow users to configure a jest.config.json file as "configFile"', () => {
+    // Arrange
+    fileExistsSyncStub.returns(true);
+    options.jest.configFile = path.resolve(projectRoot, 'jest.config.json');
+
+    // Act
+    const config = sut.loadConfig();
+
+    // Assert
+    expect(requireStub).calledWith(path.join(projectRoot, 'jest.config.json'));
+    expect(config).to.deep.contain(readConfig);
+  });
+
   it('should allow users to configure a package.json file as "configFile"', () => {
     // Arrange
     fileExistsSyncStub

packages/jest-runner/test/unit/jest-test-adapters/jest-greater-than-25-adapter.spec.ts

@@ -11,11 +11,11 @@ describe(JestGreaterThan25TestAdapter.name, () => {
   let sut: JestGreaterThan25TestAdapter;
   let runCLIStub: sinon.SinonStub;
 
-  const projectRoot = '/path/to/project';
   const fileNameUnderTest = '/path/to/file';
-  const jestConfig: Config.InitialOptions = { rootDir: projectRoot };
+  let jestConfig: Config.InitialOptions;
 
   beforeEach(() => {
+    jestConfig = { rootDir: '/path/to/project' };
     runCLIStub = sinon.stub(jestWrapper, 'runCLI');
     runCLIStub.resolves({
       config: jestConfig,
@@ -25,63 +25,69 @@ describe(JestGreaterThan25TestAdapter.name, () => {
     sut = testInjector.injector.injectClass(JestGreaterThan25TestAdapter);
   });
 
-  it('should call the runCLI method with the correct ---projectRoot', async () => {
-    await sut.run({ jestConfig, projectRoot });
-    expect(runCLIStub).calledWith(sinon.match.object, [projectRoot]);
+  it('should call the runCLI method with the correct --projectRoot', async () => {
+    await sut.run({ jestConfig });
+    expect(runCLIStub).calledWith(sinon.match.object, [jestConfig.rootDir!]);
+  });
+
+  it('should call the runCLI method with --projectRoot = cwd when no rootDir is provided', async () => {
+    delete jestConfig.rootDir;
+    await sut.run({ jestConfig });
+    expect(runCLIStub).calledWith(sinon.match.object, [process.cwd()]);
   });
 
   it('should call the runCLI method with the --findRelatedTests flag when provided', async () => {
-    await sut.run({ jestConfig, projectRoot, fileNameUnderTest });
+    await sut.run({ jestConfig, fileNameUnderTest });
 
     expect(runCLIStub).calledWith(
       sinon.match({
         $0: 'stryker',
         _: [fileNameUnderTest],
-        config: JSON.stringify({ rootDir: projectRoot }),
+        config: JSON.stringify(jestConfig),
         findRelatedTests: true,
         runInBand: true,
         silent: true,
         testNamePattern: undefined,
       }),
-      [projectRoot]
+      [jestConfig.rootDir!]
     );
   });
 
   it('should call the runCLI method with the --testNamePattern flag when provided', async () => {
-    await sut.run({ jestConfig, projectRoot, testNamePattern: 'Foo should bar' });
+    await sut.run({ jestConfig, testNamePattern: 'Foo should bar' });
 
     expect(runCLIStub).calledWith(
       sinon.match({
         $0: 'stryker',
         _: [],
-        config: JSON.stringify({ rootDir: projectRoot }),
+        config: JSON.stringify(jestConfig),
         findRelatedTests: false,
         runInBand: true,
         silent: true,
         testNamePattern: 'Foo should bar',
       }),
-      [projectRoot]
+      [jestConfig.rootDir!]
     );
   });
 
   it('should call the runCLI method with the --testLocationInResults flag when provided', async () => {
-    await sut.run({ jestConfig, projectRoot, testLocationInResults: true });
+    await sut.run({ jestConfig, testLocationInResults: true });
 
     expect(runCLIStub).calledWith(
       sinon.match({
         testLocationInResults: true,
       }),
-      [projectRoot]
+      [jestConfig.rootDir!]
     );
   });
 
   it('should call the runCLI method without the --testLocationInResults flag when not', async () => {
-    await sut.run({ jestConfig, projectRoot, testLocationInResults: false });
-    expect(runCLIStub).calledWith(sinon.match({ testLocationInResults: false }), [projectRoot]);
+    await sut.run({ jestConfig, testLocationInResults: false });
+    expect(runCLIStub).calledWith(sinon.match({ testLocationInResults: false }), [jestConfig.rootDir!]);
   });
 
   it('should call the runCLI method and return the test result', async () => {
-    const result = await sut.run({ jestConfig, projectRoot });
+    const result = await sut.run({ jestConfig });
 
     expect(result).to.deep.equal({
       config: jestConfig,
@@ -90,7 +96,7 @@ describe(JestGreaterThan25TestAdapter.name, () => {
   });
 
   it('should call the runCLI method and return the test result when run with --findRelatedTests flag', async () => {
-    const result = await sut.run({ jestConfig, projectRoot, fileNameUnderTest });
+    const result = await sut.run({ jestConfig, fileNameUnderTest });
 
     expect(result).to.deep.equal({
       config: jestConfig,

packages/jest-runner/test/unit/jest-test-runner.spec.ts

@@ -112,7 +112,7 @@ describe(JestTestRunner.name, () => {
       const sut = createSut();
       testInjector.logger.isTraceEnabled.returns(true);
       await sut.dryRun({ coverageAnalysis: 'off' });
-      expect(testInjector.logger.trace).calledWithMatch(/Invoking Jest with config\s.*/, sinon.match(/.*"jestConfig".*"projectRoot".*/));
+      expect(testInjector.logger.trace).calledWithMatch(/Invoking Jest with config\s.*/, sinon.match(/.*"jestConfig".*/));
     });
 
     it('should call the jestTestRunner run method and return a correct runResult', async () => {
@@ -481,7 +481,6 @@ describe(JestTestRunner.name, () => {
       expect(jestTestAdapterMock.run).calledWithExactly(
         sinon.match({
           jestConfig: sinon.match.object,
-          projectRoot: sinon.match.string,
           testNamePattern: undefined,
           fileNameUnderTest: '.stryker-tmp/sandbox2/foo.js',
         })
@@ -495,7 +494,6 @@ describe(JestTestRunner.name, () => {
       expect(jestTestAdapterMock.run).calledWithExactly(
         sinon.match({
           jestConfig: sinon.match.object,
-          projectRoot: sinon.match.string,
           testNamePattern: undefined,
           fileNameUnderTest: undefined,
         })

packages/jest-runner/testResources/config-in-child-dir/client/jest.config.js

@@ -0,0 +1,7 @@
+const project = "client"
+const prefix = "<rootDir>/../"
+
+module.exports = {
+  testEnvironment: "node",
+  testMatch: [prefix + project + "/**/*.test.js"],
+}

packages/jest-runner/testResources/config-in-child-dir/client/src/sum.js

@@ -0,0 +1,8 @@
+function sum(a, b) {
+  return a + b;
+}
+function sub(a, b) {
+  return a - b;
+}
+exports.sum = sum;
+exports.sub = sub;

packages/jest-runner/testResources/config-in-child-dir/client/src/sum.test.js

@@ -0,0 +1,8 @@
+const {sum, sub} = require('./sum');
+
+test('adds 1 + 2 to equal 3', () => {
+  expect(sum(1, 2)).toBe(3);
+});
+test('sub 1 - 0 to equal 1', () => {
+  expect(sub(1, 0)).toBe(1);
+});