Upstream Issue: https://github.com/karma-runner/karma/issues/1782
mediawiki-core-qunit builds have been failing since #56634. This could be fixed with a downgrade I believe.
00:19:47 Running "karma:main" (karma) task 00:19:47 06 01 2016 00:19:47.138:INFO [karma]: Karma v0.13.10 server started at http://localhost:9876/ 00:19:47 06 01 2016 00:19:47.167:INFO [launcher]: Starting browser Chrome 00:19:51 06 01 2016 00:19:51.718:INFO [Chromium 47.0.2526 (Ubuntu 0.0.0)]: Connected on socket /#e7Iz24mfR_FJ5dmQAAAA with id 6014961 00:20:01 ................................................................................ 00:20:01 ................................................................................ 00:20:05 ................................................................................ 00:20:05 ................................................................. 00:20:05 Chromium 47.0.2526 (Ubuntu 0.0.0): Executed 305 of 305 SUCCESS (7.557 secs / 7.238 secs) 00:20:05 Missing error handler on `socket`. 00:20:05 TypeError: Object [object Object] has no method 'forEach' 00:20:05 at disconnectBrowsers (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/lib/server.js:311:13) 00:20:05 at null.<anonymous> (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/lib/server.js:291:7) 00:20:05 at EventEmitter.emit (events.js:117:20) 00:20:05 at emitRunCompleteIfAllBrowsersDone (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/lib/server.js:256:12) 00:20:05 at null.<anonymous> (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/lib/server.js:278:9) 00:20:05 at EventEmitter.emit (events.js:117:20) 00:20:05 at onComplete (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/lib/browser.js:142:13) 00:20:05 at Socket.<anonymous> (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/lib/events.js:13:22) 00:20:05 at Socket.EventEmitter.emit (events.js:117:20) 00:20:05 at Socket.onevent (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/node_modules/socket.io/lib/socket.js:335:8) 00:20:05 at Socket.onpacket (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/node_modules/socket.io/lib/socket.js:295:12) 00:20:05 at Client.ondecoded (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/node_modules/socket.io/lib/client.js:193:14) 00:20:05 at Decoder.Emitter.emit (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/node_modules/socket.io/node_modules/socket.io-parser/node_modules/component-emitter/index.js:134:20) 00:20:05 at Decoder.add (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/node_modules/socket.io/node_modules/socket.io-parser/index.js:247:12) 00:20:05 at Client.ondata (/mnt/jenkins-workspace/workspace/mediawiki-core-qunit/src/node_modules/karma/node_modules/socket.io/lib/client.js:175:18) 00:20:05 at Socket.EventEmitter.emit (events.js:95:17) 00:21:05 06 01 2016 00:21:05.859:WARN [Chromium 47.0.2526 (Ubuntu 0.0.0)]: Disconnected (1 times), because no message in 60000 ms. 00:21:05 Chromium 47.0.2526 (Ubuntu 0.0.0): Executed 305 of 305 DISCONNECTED (1 min 7.573 secs / 7.238 secs) 00:21:05 Fatal error: Object [object Object] has no method 'forEach' 00:21:05 Build step 'Execute shell' marked build as failure 00:21:05 [PostBuildScript] - Execution post build scripts.