feat(jest-runner): allow configuration in a custom package.json

Add support for specifying a different `package.json` file location for your jest configuration.

For example:

```json
{
  "jest": {
      "configFile": "client/package.json"
   }
}
```

docs/jest-runner.md

@@ -9,6 +9,8 @@ Install @stryker-mutator/jest-runner locally within your project folder, like so
 
 ```bash
 npm i --save-dev @stryker-mutator/jest-runner
+# OR
+yarn add --dev @stryker-mutator/jest-runner
 ```
 
 ## Peer dependencies
@@ -59,7 +61,7 @@ Configure where jest should get its configuration from.
 
 Default: `undefined`
 
-The path to your Jest config file.
+The path to your Jest config file of package.json file containing in the `"jest"` key. By default, the @stryker-mutator/jest-runner will try to look for "jest.conf.js" or "package.json" in the current working directory.
 
 ### `jest.config` [`object`]
 
@@ -80,15 +82,7 @@ The `@stryker-mutator/jest-runner` plugin supports coverage analysis and test fi
 
 ### Coverage reporting
 
-When using `"all"` or `"perTest"` coverage analysis, this plugin reports mutant coverage by hooking into the [jest's test environment](https://jestjs.io/docs/en/configuration.html#testenvironment-string). The test environment setting is overridden based on the `"testEnvironment"` configuration option in your jest config:
-
-Jest test environment|Jest runner's override|
----|---
-node|@stryker-mutator/jest-runner/jest-env/node
-jsdom|@stryker-mutator/jest-runner/jest-env/jsom
-jest-environment-jsdom-sixteen|@stryker-mutator/jest-runner/jest-env/jsom-sixteen
-
-As long as you're using one of these test environments, you won't have to do anything.
+When using `"all"` or `"perTest"` coverage analysis, this plugin reports mutant coverage by hooking into the [jest's test environment](https://jestjs.io/docs/en/configuration.html#testenvironment-string). The test environment setting in your configuration file is overridden by default and you won't have to do anything here.
 
 However, if you choose to override the jest-environment on a file-by-file basis using [jest's `@jest-environment` docblock](https://jestjs.io/docs/en/configuration.html#testenvironment-string), you will have to do the work. 
 
@@ -108,6 +102,14 @@ Becomes:
  */
 ```
 
+This is the list of jest environments that are shipped with @stryker-mutator/jest-runner.
+
+Jest test environment|@stryker-mutator/jest-runner override|
+---|---
+node|@stryker-mutator/jest-runner/jest-env/node
+jsdom|@stryker-mutator/jest-runner/jest-env/jsom
+jest-environment-jsdom-sixteen|@stryker-mutator/jest-runner/jest-env/jsom-sixteen
+
 Don't worry; using Stryker's alternative is harmless during regular unit testing.
 
 If you're using a custom test environment, you'll need to mixin the Stryker functionality yourself:
@@ -126,6 +128,6 @@ module.exports = mixinJestEnvironment(MyCustomTestEnvironment);
 
 ### Test filtering
 
-When using `"perTest"` coverage analysis, the `@stryker-mutator/jest-runner` will hook into the [jest test runner](https://jestjs.io/docs/en/configuration.html#testrunner-string). Both the default `"jasmine2"` as well as [jest-circus](https://www.npmjs.com/package/jest-circus) are supported here. 
+When using `"perTest"` coverage analysis, the `@stryker-mutator/jest-runner` will hook into the [jest test runner](https://jestjs.io/docs/en/configuration.html#testrunner-string). Both `"jasmine2"` as well as [`jest-circus`](https://www.npmjs.com/package/jest-circus) (default) are supported here. 
 
 If you're using a different test runner, you're out of luck. Please downgrade to using `"all"` coverage analysis. If you think we should support your test runner, please let us know by opening an [issue](https://github.com/stryker-mutator/stryker-js/issues/new?assignees=&labels=%F0%9F%9A%80+Feature+request&template=feature_request.md&title=), or by joining our [slack channel](https://join.slack.com/t/stryker-mutator/shared_invite/enQtOTUyMTYyNTg1NDQ0LTU4ODNmZDlmN2I3MmEyMTVhYjZlYmJkOThlNTY3NTM1M2QxYmM5YTM3ODQxYmJjY2YyYzllM2RkMmM1NjNjZjM).

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

@@ -6,50 +6,66 @@ import { tokens, commonTokens } from '@stryker-mutator/api/plugin';
 import { StrykerOptions } from '@stryker-mutator/api/core';
 import { Config } from '@jest/types';
 
-import { loader, projectRoot } from '../plugin-tokens';
+import { requireResolve } from '@stryker-mutator/util';
+
 import { JestRunnerOptionsWithStrykerOptions } from '../jest-runner-options-with-stryker-options';
 
 import { JestConfigLoader } from './jest-config-loader';
-import { NodeRequireFunction } from './node-require-function';
 
 /**
  * The Default config loader will load the Jest configuration using the package.json in the package root
  */
 export class CustomJestConfigLoader implements JestConfigLoader {
-  public static inject = tokens(commonTokens.logger, commonTokens.options, loader, projectRoot);
+  public static inject = tokens(commonTokens.logger, commonTokens.options);
 
-  constructor(
-    private readonly log: Logger,
-    private readonly options: StrykerOptions,
-    private readonly require: NodeRequireFunction,
-    private readonly root: string
-  ) {}
+  constructor(private readonly log: Logger, private readonly options: StrykerOptions) {}
 
   public loadConfig(): Config.InitialOptions {
-    const jestConfig = this.readConfigFromJestConfigFile() || this.readConfigFromPackageJson() || {};
+    const jestConfig = this.readConfigFromJestConfigFile() ?? this.readConfigFromPackageJson() ?? {};
+    this.log.debug('Final jest config: %s', jestConfig);
     return jestConfig;
   }
 
-  private readConfigFromJestConfigFile() {
-    try {
-      const jestOptions = this.options as JestRunnerOptionsWithStrykerOptions;
-      const configFilePath = path.join(this.root, jestOptions.jest?.configFile ?? 'jest.config.js');
-      const config = this.require(configFilePath);
+  private readConfigFromJestConfigFile(): Config.InitialOptions | undefined {
+    const configFilePath = this.resolveJestConfigFilePath();
+    if (configFilePath) {
+      const config = requireResolve(configFilePath) as Config.InitialOptions;
       this.log.debug(`Read Jest config from ${configFilePath}`);
+      this.setRootDir(config, configFilePath);
       return config;
-    } catch {
-      /* Don't return anything (implicitly return undefined) */
     }
+    return undefined;
   }
 
-  private readConfigFromPackageJson() {
-    try {
-      const configFilePath = path.join(this.root, 'package.json');
-      const config = JSON.parse(fs.readFileSync(configFilePath, 'utf8')).jest;
-      this.log.debug(`Read Jest config from ${configFilePath}`);
+  private readConfigFromPackageJson(): Config.InitialOptions | undefined {
+    const pkgJsonFilePath = this.resolvePackageJsonFilePath();
+    if (pkgJsonFilePath) {
+      const config: Config.InitialOptions = JSON.parse(fs.readFileSync(pkgJsonFilePath, 'utf8')).jest ?? {};
+      this.log.debug(`Read Jest config from ${pkgJsonFilePath}`);
+      this.setRootDir(config, pkgJsonFilePath);
       return config;
-    } catch {
-      /* Don't return anything (implicitly return undefined) */
     }
+    return undefined;
+  }
+
+  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))) {
+      return packageJsonCandidate;
+    }
+    return undefined;
+  }
+  private setRootDir(config: Config.InitialOptions, configFilePath: string) {
+    config.rootDir = path.resolve(path.dirname(configFilePath), config.rootDir ?? '.');
+  }
+
+  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))) {
+      return configFileCandidate;
+    }
+    return undefined;
   }
 }

packages/jest-runner/src/config-loaders/index.ts

@@ -2,8 +2,6 @@ import { tokens, commonTokens, Injector, PluginContext } from '@stryker-mutator/
 import { StrykerOptions } from '@stryker-mutator/api/core';
 import { Logger } from '@stryker-mutator/api/logging';
 
-import { requireResolve } from '@stryker-mutator/util';
-
 import { JestRunnerOptionsWithStrykerOptions } from '../jest-runner-options-with-stryker-options';
 import * as pluginTokens from '../plugin-tokens';
 
@@ -22,11 +20,7 @@ export function configLoaderFactory(
     }
   };
   const optionsWithJest: JestRunnerOptionsWithStrykerOptions = options as JestRunnerOptionsWithStrykerOptions;
-
-  const configLoaderInjector = injector
-    .provideValue(pluginTokens.loader, requireResolve)
-    .provideValue(pluginTokens.resolve, require.resolve)
-    .provideValue(pluginTokens.projectRoot, process.cwd());
+  const configLoaderInjector = injector.provideValue(pluginTokens.resolve, require.resolve);
 
   switch (optionsWithJest.jest.projectType) {
     case 'custom':

packages/jest-runner/src/config-loaders/react-scripts-jest-config-loader.ts

@@ -3,28 +3,32 @@ import path from 'path';
 import { tokens } from '@stryker-mutator/api/plugin';
 import { Config } from '@jest/types';
 
-import { createReactJestConfig } from '../utils';
+import { PropertyPathBuilder, requireResolve } from '@stryker-mutator/util';
+
 import * as pluginTokens from '../plugin-tokens';
+import { JestRunnerOptionsWithStrykerOptions } from '../jest-runner-options-with-stryker-options';
 
 import { JestConfigLoader } from './jest-config-loader';
 
 export class ReactScriptsJestConfigLoader implements JestConfigLoader {
-  public static inject = tokens(pluginTokens.resolve, pluginTokens.projectRoot);
+  public static inject = tokens(pluginTokens.resolve);
 
-  constructor(private readonly resolve: RequireResolve, private readonly projectRoot: string) {}
+  constructor(private readonly resolve: RequireResolve) {}
 
   public loadConfig(): Config.InitialOptions {
     try {
-      // Get the location of react script, this is later used to generate the Jest configuration used for React projects.
-      const reactScriptsLocation = path.join(this.resolve('react-scripts/package.json'), '..');
-
       // Create the React configuration for Jest
-      const jestConfiguration = this.createJestConfig(reactScriptsLocation);
+      const jestConfiguration = this.createJestConfig();
 
       return jestConfiguration;
     } catch (e) {
       if (this.isNodeErrnoException(e) && e.code === 'MODULE_NOT_FOUND') {
-        throw Error('Unable to locate package react-scripts. This package is required when projectType is set to "create-react-app".');
+        throw Error(
+          `Unable to locate package "react-scripts". This package is required when "${PropertyPathBuilder.create<JestRunnerOptionsWithStrykerOptions>()
+            .prop('jest')
+            .prop('projectType')
+            .build()}" is set to "create-react-app".`
+        );
       }
       throw e;
     }
@@ -34,7 +38,13 @@ export class ReactScriptsJestConfigLoader implements JestConfigLoader {
     return arg.code !== undefined;
   }
 
-  private createJestConfig(reactScriptsLocation: string): Config.InitialOptions {
-    return createReactJestConfig((relativePath: string): string => path.join(reactScriptsLocation, relativePath), this.projectRoot, false);
+  private createJestConfig(): Config.InitialOptions {
+    const createReactJestConfig = requireResolve('react-scripts/scripts/utils/createJestConfig') as (
+      resolve: (thing: string) => string,
+      rootDir: string,
+      isEjecting: boolean
+    ) => Config.InitialOptions;
+    const reactScriptsLocation = path.join(this.resolve('react-scripts/package.json'), '..');
+    return createReactJestConfig((relativePath) => path.join(reactScriptsLocation, relativePath), process.cwd(), false);
   }
 }

packages/jest-runner/test/helpers/producers.ts

@@ -1,9 +1,15 @@
 import type { TestResult, AggregatedResult, AssertionResult, SerializableError } from '@jest/test-result';
 import type { EnvironmentContext } from '@jest/environment';
 import { Circus, Config } from '@jest/types';
+import { factory } from '@stryker-mutator/test-helpers';
 
 import { JestOptions } from '../../src-generated/jest-runner-options';
 import { JestRunResult } from '../../src/jest-run-result';
+import { JestRunnerOptionsWithStrykerOptions } from '../../src/jest-runner-options-with-stryker-options';
+
+export const createJestRunnerOptionsWithStrykerOptions = (overrides?: Partial<JestOptions>): JestRunnerOptionsWithStrykerOptions => {
+  return factory.strykerWithPluginOptions({ jest: createJestOptions(overrides) });
+};
 
 export const createJestOptions = (overrides?: Partial<JestOptions>): JestOptions => {
   return {