Make a single file with all tests for karma to consume

karma.conf.js

// Simplified config file
const path = require('path');
const junitOutput = process.env.CIRCLE_TEST_REPORTS || 'junit'

module.exports = function (config) {
  config.set({

    port: 9876,

    logLevel: config.LOG_INFO,

    browsers: ['PhantomJS'],

    frameworks: ['jasmine', 'sinon', 'browserify'],

    reporters: ['spec'],
    
    files: [{
      pattern: 'tests.webpack.js'
    }],
    
    preprocessors: {
      'tests.webpack.js': ['webpack', 'sourcemap']
    }
  });
};

tests.webpack.js

(function() {
  // require all modules ending in ".test.js" from the
  // current directory and all subdirectories
  var specs = require.context('./app', true, /\.spec\.js$/),
      actions = require.context('./app/actions', true, /\.js$/),
      components = require.context('./app/components', true, /\.js$/),
      containers = require.context('./app/containers', true, /\.js$/),
      reducers = require.context('./app/reducers', true, /\.js$/),
      utils = require.context('./app/utils', true, /\.js$/);

  [
    specs,
    actions,
    components,
    containers,
    reducers,
    utils
  ].forEach(function(type) {
    type.keys().forEach(type);
  });
}());