karma.config.js

const browsers = require('./browsers');

const isBench = process.env.BENCHMARK === 'true';
const useCloud = process.env.USE_CLOUD === 'true';
const browserStackUserName = process.env.BROWSER_STACK_USERNAME;
const browserStackAccessKey = process.env.BROWSER_STACK_ACCESS_KEY;
const isTravis = process.env.TRAVIS;
const travisBuildNumber = process.env.TRAVIS_BUILD_NUMBER;
const travisBuildId = process.env.TRAVIS_BUILD_ID;
const travisJobNumber = process.env.TRAVIS_JOB_NUMBER;

module.exports = (config) => {
  config.set({
    customLaunchers: browsers,
    browsers: ['Chrome'],
    frameworks: ['mocha'],
    files: [
      './src/*.test.js',
    ],
    preprocessors: {
      './src/*.js': ['rollup', 'sourcemap'],
    },
    reporters: ['mocha', 'coverage'],
    coverageReporter: {
      dir: 'coverage',
      file: 'coverage.json',
      type: 'json',
    },
  });

  if (isBench) {
    Object.assign(config, {
      browsers: ['Chrome'],
      frameworks: ['benchmark'],
      // Using a fixed position for a file name, m.b. should use an args parser later.
      files: [process.argv[4] || 'benchmark/*.js'],
      preprocessors: { 'benchmark/*.js': ['rollup'] },
      reporters: ['benchmark'],
      // Some tests are slow.
      browserNoActivityTimeout: 20000,
    });
  }

  if (useCloud) {
    Object.assign(config, {
      browsers: Object.keys(browsers),
      browserDisconnectTolerance: 3,
      // My current OS plan allows max 2 parallel connections.
      concurrency: 2,
      retryLimit: 3,
      browserStack: {
        username: browserStackUserName,
        accessKey: browserStackAccessKey,
        captureTimeout: 10000,
      },
    });

    if (isTravis) {
      Object.assign(config.browserStack, {
        build: `TRAVIS #${travisBuildNumber} (${travisBuildId})`,
        name: travisJobNumber,
      });
    }
  }
};