Upgrade Jest to 17.0 (#1078)

* Replace `scriptPreprocessor` config with `transform`.
* Also remove `moduleFileExtensions` which has been redundant since 16.0
  (`['js', 'json', 'jsx', 'node’]` is the default)

packages/react-scripts/package.json

@@ -26,7 +26,7 @@
     "autoprefixer": "6.5.1",
     "babel-core": "6.17.0",
     "babel-eslint": "7.0.0",
-    "babel-jest": "16.0.0",
+    "babel-jest": "17.0.2",
     "babel-loader": "6.2.7",
     "babel-preset-react-app": "^1.0.0",
     "case-sensitive-paths-webpack-plugin": "1.1.4",
@@ -50,7 +50,7 @@
     "gzip-size": "3.0.0",
     "html-webpack-plugin": "2.24.0",
     "http-proxy-middleware": "0.17.2",
-    "jest": "16.0.2",
+    "jest": "17.0.2",
     "json-loader": "0.5.4",
     "object-assign": "4.1.0",
     "path-exists": "2.1.0",

packages/react-scripts/utils/createJestConfig.js

@@ -19,7 +19,6 @@ module.exports = (resolve, rootDir, isEjecting) => {
 
   const config = {
     collectCoverageFrom: ['src/**/*.{js,jsx}'],
-    moduleFileExtensions: ['jsx', 'js', 'json'],
     moduleNameMapper: {
       '^.+\\.(ico|jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$': resolve('config/jest/FileStub.js'),
       '^.+\\.css$': resolve('config/jest/CSSStub.js')
@@ -35,7 +34,9 @@ module.exports = (resolve, rootDir, isEjecting) => {
   if (!isEjecting) {
     // This is unnecessary after ejecting because Jest
     // will just use .babelrc in the project folder.
-    config.scriptPreprocessor = resolve('config/jest/transform.js');
+    config.transform = {
+      '^.+\\.(js|jsx)$': resolve('config/jest/transform.js'),
+    };
   }
   return config;
 };