Karma 4.0.1 fails with unexpected identifier 'async'

Expected behaviour

karma 4.0.1 to start the test and successfully test out the specs. While it works fine locally (osx), for some reason it’s failing in CI environment.

Actual behaviour

#!/bin/bash -eo pipefail
cd spec_js
if [ "$CIRCLE_NODE_INDEX" -eq 2 ]; then npm install && npm run test-ci; fi
npm notice created a lockfile as package-lock.json. You should commit this file.
npm WARN app@0.0.1 No repository field.
npm WARN app@0.0.1 No license field.
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.7 (node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.7: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})

added 372 packages in 10.533s

> app@0.0.1 test-ci /home/circleci/project/spec_js
> ./node_modules/karma/bin/karma start ./karma.conf.js

/home/circleci/project/spec_js/node_modules/karma/lib/server.js:118
async start () {
^^^^^
SyntaxError: Unexpected identifier
at exports.runInThisContext (vm.js:53:16)
at Module._compile (module.js:511:25)
at Object.Module._extensions..js (module.js:550:10)
at Module.load (module.js:456:32)
at tryModuleLoad (module.js:415:12)
at Function.Module._load (module.js:407:3)
at Module.require (module.js:466:17)
at require (internal/module.js:20:19)
at Object.<anonymous> (/home/circleci/project/spec_js/node_modules/karma/lib/cli.js:8:16)
at Module._compile (module.js:541:32)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! app@0.0.1 test-ci: `./node_modules/karma/bin/karma start ./karma.conf.js`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the app@0.0.1 test-ci script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/circleci/.npm/_logs/2019-03-15T05_32_20_835Z-debug.log
Exited with code 1

Environment Details

• Node v11.6.0 (npm v6.5.0-next.0)
• Karma - 4.0.1
• Relevant part of your karma.config.js file

/// karma.conf.js
module.exports = function (config) {
  config.set({
    basePath: '',
    frameworks: ['mocha', 'chai', 'sinon'],
    plugins: [
      'karma-chrome-launcher',
      'karma-mocha',
      'karma-chai',
      'karma-sinon',
      'karma-string-replace-preprocessor'
    ],
    files: [
      'jquery.js',
      '../pages.js',
      'pages-spec.js'
    ],
    exclude: [],
    preprocessors: {
      '../pages.js': ['stringreplace']
    },
    stringReplacePreprocessor: {
      patterns: [
        { match: 'process.env.HOST', replacement: '"https://www.host.com"' },
      ]
    },
    reporters: ['progress'],
    port: 9876,
    colors: true,
    logLevel: config.LOG_INFO,
    autoWatch: false,
    browsers: ['Chrome'],
    singleRun: true
  });
};

[johnjbarton]

The most likely explanation is that your CircleCI is running node < 6.

[johnjbarton]

@yrtimiD Use karma 3.x for node 6.x.