karma.conf.js

module.exports = function(config) {
  var root = 'target/public/dev'// same as :output-dir

  config.set({
    frameworks: ['cljs-test'],

    files: [
      root + '/goog/base.js',
      root + '/cljs_deps.js',
      root + '/app.js',// same as :output-to
      {pattern: root + '/*.js', included: false},
      {pattern: root + '/**/*.js', included: false}
    ],

    client: {
      // main function
      args: ['app.test_runner.run']
    },

    // singleRun set to false does not work!
    singleRun: true,
    
    // ------------------
    // coverage
    // ------------------
    
    reporters: ['progress', 'coverage'],
    
    coverageReporter: {
      dir: 'target/coverage',
      reporters: [
        // cljs->js coverage (just in case you are curious as I am)
        {type: 'html', subdir: 'report-html'},
        // run
        // ./node_modules/.bin/remap-istanbul -i target/coverage/report-json/coverage.json -o target/coverage/report-html-final -t html
        // to generate cljs code coverage
        {type: 'json', subdir: 'report-json', file: 'coverage.json'}
      ]
    },

    // collect coverage only for my code
    // (as I'm not interested in goog, cljs, clojure, etc. namespaces/dirs)
    preprocessors: {
      'target/public/dev/<root_namespace>/**/*.js': ['coverage']
    },
  })
}