add custom mocha reporter

build-system/tasks/e2e/index.js

@@ -24,12 +24,14 @@ const fs = require('fs');
 const glob = require('glob');
 const http = require('http');
 const Mocha = require('mocha');
+const MochaJUnitReporter = require('mocha-junit-reporter');
 const path = require('path');
 const {
   createCtrlcHandler,
   exitCtrlcHandler,
 } = require('../../common/ctrlcHandler');
 const {buildRuntime, getFilesFromArgv} = require('../../common/utils');
+const {createMultiplexedReporter} = require('./mocha-report-multiplexer');
 const {cyan} = require('kleur/colors');
 const {execOrDie} = require('../../common/exec');
 const {HOST, PORT, startServer, stopServer} = require('../serve');
@@ -96,7 +98,10 @@ function createMocha_() {
   };
 
   if (isCircleciBuild()) {
-    options.reporter = 'mocha-junit-reporter';
+    options.reporter = createMultiplexedReporter([
+      options.reporter,
+      MochaJUnitReporter,
+    ]);
     options.reporterOptions = {
       mochaFile: 'result-reports/e2e.xml',
     };

build-system/tasks/e2e/mocha-report-multiplexer.js

@@ -0,0 +1,48 @@
+/**
+ * Copyright 2021 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+const Mocha = require('mocha');
+const {Base} = Mocha.reporters;
+
+/**
+ * Creates a custom Mocha reporter which runs many reporters at once.
+ * @param {Base[]} reporters
+ * @return {Function<*,MochaReportMultiplexer>}
+ */
+function createMultiplexedReporter(reporters) {
+  return class DynamicReportMultiplexer extends Base {
+    /**
+     * @param {*} runner
+     * @param {Mocha.Runner.options} options
+     */
+    constructor(runner, options) {
+      super(runner);
+      // If there are too many reporters listening to events on the runner a
+      // warning will be displayed about a potential emitter leak. This should
+      // allow each reporter to listen to every event without exceeding the max.
+      // The default max listeners is 10.
+      const potentialEvents = Object.keys(Mocha.Runner.constants);
+      runner.setMaxListeners(potentialEvents.length * reporters.length);
+
+      this.reporters = reporters.map(
+        (reporter) => new reporter(runner, options)
+      );
+    }
+  };
+}
+
+module.exports = {
+  createMultiplexedReporter,
+};

build-system/test-configs/karma.conf.js

@@ -80,10 +80,6 @@ module.exports = {
     },
   },
 
-  junitReporter: {
-    useBrowserName: false,
-  },
-
   port: 9876,
 
   colors: true,