Add overrideConfig option for the react-scripts test script

packages/react-scripts/scripts/test.js

@@ -20,6 +20,7 @@ require('dotenv').config({silent: true});
 
 const jest = require('jest');
 const argv = process.argv.slice(2);
+const overrideArg = (process.argv.filter((i) => i.match('--overrideConfig')) || [])[0];
 
 // Watch unless on CI or in coverage mode
 if (!process.env.CI && argv.indexOf('--coverage') < 0) {
@@ -31,10 +32,17 @@ if (!process.env.CI && argv.indexOf('--coverage') < 0) {
 const createJestConfig = require('../utils/createJestConfig');
 const path = require('path');
 const paths = require('../config/paths');
+
+var overrideConfig;
+if ( overrideArg ) {
+  overrideConfig = require(path.resolve(paths.appSrc, '..', overrideArg.split('=')[1] ));
+}
+
 argv.push('--config', JSON.stringify(createJestConfig(
   relativePath => path.resolve(__dirname, '..', relativePath),
   path.resolve(paths.appSrc, '..'),
-  false
+  false,
+  overrideConfig
 )));
 // @remove-on-eject-end
 jest.run(argv);

packages/react-scripts/template/README.md

@@ -156,6 +156,9 @@ You will also see any lint errors in the console.
 Launches the test runner in the interactive watch mode.<br>
 See the section about [running tests](#running-tests) for more information.
 
+You can add your own test configuration by specifying a json file using '--overrideConfig'.
+This will also override existing react-scripts configuration.
+
 ### `npm run build`
 
 Builds the app for production to the `build` folder.<br>

packages/react-scripts/utils/createJestConfig.js

@@ -12,7 +12,7 @@
 const fs = require('fs');
 const paths = require('../config/paths');
 
-module.exports = (resolve, rootDir, isEjecting) => {
+module.exports = (resolve, rootDir, isEjecting, overrides) => {
   // Use this instead of `paths.testsSetup` to avoid putting
   // an absolute filename into configuration after ejecting.
   const setupTestsFile = fs.existsSync(paths.testsSetup) ? '<rootDir>/src/setupTests.js' : undefined;
@@ -45,5 +45,12 @@ module.exports = (resolve, rootDir, isEjecting) => {
   if (rootDir) {
     config.rootDir = rootDir;
   }
+
+  if( overrides ) {
+    Object.keys(overrides).forEach((k) => {
+      config[k] = overrides[k];
+    });
+  }
+
   return config;
 };