Fix memory and performance issues in Karma test suite

config/karma.config.js

-var path = require('path');
-var webpack = require('webpack');
-var argumentsParser = require('commander');
-var webpackConfig = require('./webpack.config.js');
-var ROOT_PATH = path.resolve(__dirname, '..');
+const path = require('path');
+const glob = require('glob');
+const chalk = require('chalk');
+const webpack = require('webpack');
+const argumentsParser = require('commander');
+const webpackConfig = require('./webpack.config.js');
+
+const ROOT_PATH = path.resolve(__dirname, '..');
+
+function fatalError(message) {
+  console.error(chalk.red(`\nError: ${message}\n`));
+  process.exit(1);
+}
 // remove problematic plugins
 if (webpackConfig.plugins) {
@@ -15,33 +23,70 @@ if (webpackConfig.plugins) {
   });
 }
-var testFiles = argumentsParser
+const specFilters = argumentsParser
   .option(
     '-f, --filter-spec [filter]',
     'Filter run spec files by path. Multiple filters are like a logical OR.',
-    (val, memo) => {
-      memo.push(val);
+    (filter, memo) => {
+      memo.push(filter, filter.replace(/\/?$/, '/**/*.js'));
       return memo;
     },
     []
   )
   .parse(process.argv).filterSpec;
-webpackConfig.plugins.push(
-  new webpack.DefinePlugin({
-    'process.env.TEST_FILES': JSON.stringify(testFiles),
-  })
-);
-webpackConfig.devtool = process.env.BABEL_ENV !== 'coverage' && 'cheap-inline-source-map';
+if (specFilters.length) {
+  const specsPath = /^(?:\.[\\\/])?spec[\\\/]javascripts[\\\/]/;
+
+  // resolve filters
+  let filteredSpecFiles = specFilters.map(filter =>
+    glob
+      .sync(filter, {
+        root: ROOT_PATH,
+        matchBase: true,
+      })
+      .filter(path => path.endsWith('spec.js'))
+  );
+
+  // flatten
+  filteredSpecFiles = Array.prototype.concat.apply([], filteredSpecFiles);
+
+  // remove duplicates
+  filteredSpecFiles = [...new Set(filteredSpecFiles)];
+
+  if (filteredSpecFiles.length < 1) {
+    fatalError('Your filter did not match any test files.');
+  }
+
+  if (!filteredSpecFiles.every(file => specsPath.test(file))) {
+    fatalError('Test files must be located within /spec/javascripts.');
+  }
+
+  const newContext = filteredSpecFiles.reduce((context, file) => {
+    const relativePath = file.replace(specsPath, '');
+    context[file] = `./${relativePath}`;
+    return context;
+  }, {});
+
+  webpackConfig.plugins.push(
+    new webpack.ContextReplacementPlugin(
+      /spec[\\\/]javascripts$/,
+      path.join(ROOT_PATH, 'spec/javascripts'),
+      newContext
+    )
+  );
+}
+webpackConfig.entry = undefined;
+webpackConfig.devtool = 'cheap-inline-source-map';
 // Karma configuration
 module.exports = function(config) {
   process.env.TZ = 'Etc/UTC';
-  var progressReporter = process.env.CI ? 'mocha' : 'progress';
-  var karmaConfig = {
+  const progressReporter = process.env.CI ? 'mocha' : 'progress';
+  const karmaConfig = {
     basePath: ROOT_PATH,
     browsers: ['ChromeHeadlessCustom'],
     customLaunchers: {

config/webpack.config.js

@@ -69,6 +69,9 @@ const config = {
         test: /\.js$/,
         exclude: /(node_modules|vendor\/assets)/,
         loader: 'babel-loader',
+        options: {
+          cacheDirectory: path.join(ROOT_PATH, 'tmp/cache/babel-loader'),
+        },
       },
       {
         test: /\.vue$/,

doc/development/testing_guide/frontend_testing.md

@@ -62,6 +62,7 @@ describe('.methodName', () => {
   });
 });
 ```
+
 #### Testing promises
 When testing Promises you should always make sure that the test is asynchronous and rejections are handled.
@@ -69,9 +70,9 @@ Your Promise chain should therefore end with a call of the `done` callback and `
 ```javascript
 // Good
-it('tests a promise', (done) => {
+it('tests a promise', done => {
   promise
-    .then((data) => {
+    .then(data => {
       expect(data).toBe(asExpected);
     })
     .then(done)
@@ -79,10 +80,10 @@ it('tests a promise', (done) => {
 });
 // Good
-it('tests a promise rejection', (done) => {
+it('tests a promise rejection', done => {
   promise
     .then(done.fail)
-    .catch((error) => {
+    .catch(error => {
       expect(error).toBe(expectedError);
     })
     .then(done)
@@ -91,38 +92,37 @@ it('tests a promise rejection', (done) => {
 // Bad (missing done callback)
 it('tests a promise', () => {
-  promise
-    .then((data) => {
-      expect(data).toBe(asExpected);
-    })
+  promise.then(data => {
+    expect(data).toBe(asExpected);
+  });
 });
 // Bad (missing catch)
-it('tests a promise', (done) => {
+it('tests a promise', done => {
   promise
-    .then((data) => {
+    .then(data => {
       expect(data).toBe(asExpected);
     })
-    .then(done)
+    .then(done);
 });
 // Bad (use done.fail in asynchronous tests)
-it('tests a promise', (done) => {
+it('tests a promise', done => {
   promise
-    .then((data) => {
+    .then(data => {
       expect(data).toBe(asExpected);
     })
     .then(done)
-    .catch(fail)
+    .catch(fail);
 });
 // Bad (missing catch)
-it('tests a promise rejection', (done) => {
+it('tests a promise rejection', done => {
   promise
-    .catch((error) => {
+    .catch(error => {
       expect(error).toBe(expectedError);
     })
-    .then(done)
+    .then(done);
 });
 ```
@@ -139,7 +139,7 @@ documentation for these methods can be found in the [jasmine introduction page](
 Sometimes you may need to spy on a method that is directly imported by another
 module. GitLab has a custom `spyOnDependency` method which utilizes
 [babel-plugin-rewire](https://github.com/speedskater/babel-plugin-rewire) to
-achieve this.  It can be used like so:
+achieve this. It can be used like so:
 ```javascript
 // my_module.js
@@ -181,8 +181,8 @@ See this [section][vue-test].
 `rake karma` runs the frontend-only (JavaScript) tests.
 It consists of two subtasks:
-- `rake karma:fixtures` (re-)generates fixtures
-- `rake karma:tests` actually executes the tests
+* `rake karma:fixtures` (re-)generates fixtures
+* `rake karma:tests` actually executes the tests
 As long as the fixtures don't change, `rake karma:tests` (or `yarn karma`)
 is sufficient (and saves you some time).
@@ -217,6 +217,14 @@ yarn karma-start --filter-spec profile/account/components/
 yarn karma-start -f vue_shared -f vue_mr_widget
 ```
+You can also use glob syntax to match files. Remember to put quotes around the
+glob otherwise your shell may split it into multiple arguments:
+
+```bash
+# Run all specs named `file_spec` within the IDE subdirectory
+yarn karma -f 'spec/javascripts/ide/**/file_spec.js'
+```
+
 ## RSpec feature integration tests
 Information on setting up and running RSpec integration tests with
@@ -231,14 +239,14 @@ supported by the PhantomJS test runner which is used for both Karma and RSpec
 tests. We polyfill some JavaScript objects for older browsers, but some
 features are still unavailable:
-- Array.from
-- Array.first
-- Async functions
-- Generators
-- Array destructuring
-- For..Of
-- Symbol/Symbol.iterator
-- Spread
+* Array.from
+* Array.first
+* Async functions
+* Generators
+* Array destructuring
+* For..Of
+* Symbol/Symbol.iterator
+* Spread
 Until these are polyfilled appropriately, they should not be used. Please
 update this list with additional unsupported features.
@@ -295,11 +303,11 @@ Scenario: Developer can approve merge request
 [jasmine-focus]: https://jasmine.github.io/2.5/focused_specs.html
 [jasmine-jquery]: https://github.com/velesin/jasmine-jquery
 [karma]: http://karma-runner.github.io/
-[vue-test]:https://docs.gitlab.com/ce/development/fe_guide/vue.html#testing-vue-components
-[RSpec]: https://github.com/rspec/rspec-rails#feature-specs
-[Capybara]: https://github.com/teamcapybara/capybara
-[Karma]: http://karma-runner.github.io/
-[Jasmine]: https://jasmine.github.io/
+[vue-test]: https://docs.gitlab.com/ce/development/fe_guide/vue.html#testing-vue-components
+[rspec]: https://github.com/rspec/rspec-rails#feature-specs
+[capybara]: https://github.com/teamcapybara/capybara
+[karma]: http://karma-runner.github.io/
+[jasmine]: https://jasmine.github.io/
 ---

package.json

@@ -98,10 +98,11 @@
   "devDependencies": {
     "axios-mock-adapter": "^1.10.0",
     "babel-eslint": "^8.0.2",
-    "babel-plugin-istanbul": "^4.1.5",
+    "babel-plugin-istanbul": "^4.1.6",
     "babel-plugin-rewire": "^1.1.0",
     "babel-template": "^6.26.0",
     "babel-types": "^6.26.0",
+    "chalk": "^2.4.1",
     "commander": "^2.15.1",
     "eslint": "^3.18.0",
     "eslint-config-airbnb-base": "^10.0.1",
@@ -116,13 +117,13 @@
     "istanbul": "^0.4.5",
     "jasmine-core": "^2.9.0",
     "jasmine-jquery": "^2.1.1",
-    "karma": "^2.0.0",
+    "karma": "^2.0.2",
     "karma-chrome-launcher": "^2.2.0",
-    "karma-coverage-istanbul-reporter": "^1.4.1",
+    "karma-coverage-istanbul-reporter": "^1.4.2",
     "karma-jasmine": "^1.1.1",
     "karma-mocha-reporter": "^2.2.5",
     "karma-sourcemap-loader": "^0.3.7",
-    "karma-webpack": "2.0.7",
+    "karma-webpack": "3.0.0",
     "nodemon": "^1.15.1",
     "prettier": "1.11.1",
     "webpack-dev-server": "^2.11.2"

spec/javascripts/test_bundle.js

@@ -84,21 +84,11 @@ beforeEach(() => {
 const axiosDefaultAdapter = getDefaultAdapter();
-let testFiles = process.env.TEST_FILES || [];
-if (testFiles.length > 0) {
-  testFiles = testFiles.map(path => path.replace(/^spec\/javascripts\//, '').replace(/\.js$/, ''));
-  console.log(`Running only tests matching: ${testFiles}`);
-} else {
-  console.log('Running all tests');
-}
-
 // render all of our tests
 const testsContext = require.context('.', true, /_spec$/);
 testsContext.keys().forEach(function(path) {
   try {
-    if (testFiles.length === 0 || testFiles.some(p => path.includes(p))) {
-      testsContext(path);
-    }
+    testsContext(path);
   } catch (err) {
     console.error('[ERROR] Unable to load spec: ', path);
     describe('Test bundle', function() {