Karma coverage always coming empty

I've been trying to run karma coverage for a couple of days now only to find an empty blank page as below.

Here's my configuration:

var path = require('path');

var webpackConfig = require('./webpack.common');

module.exports = function (config) {
  var _config = {
    basePath: '',
    frameworks: ['jasmine'],
    files: [
      { pattern: './karma-shim.js', watched: false }
    ],
    exclude: [],
    preprocessors: {
      './karma-shim.js': ['webpack', 'sourcemap', 'coverage']
    },
    client: {
      captureConsole: false
    },
    webpack: webpackConfig,

    webpackMiddleware: {
      stats: 'errors-only'
    },

    coverageReporter: {
      dir: 'coverage/',
      reporters: [{
        type: 'json',
        dir: 'coverage',
        subdir: 'json',
        file: 'coverage-final.json'
      }]
    },

    remapIstanbulReporter: {
      src: 'coverage/json/coverage-final.json',
      reports: {
        lcovonly: 'coverage/json/lcov.info',
        html: 'coverage/html',
        'text': null
      },
      timeoutNotCreated: 1000, // default value
      timeoutNoMoreFiles: 1000 // default value
    },

    webpackServer: {
      noInfo: true // please don't spam the console when running in karma!
    },
    reporters: ["mocha", "coverage", "karma-remap-istanbul"],
    port: 9876,
    colors: true,
    logLevel: config.LOG_ERROR,
    autoWatch: false,
    browsers: ['PhantomJS'], // you can also use Chrome

    singleRun: true
  };

  config.set(_config);

};

And here's my karma-shim.js file

Error.stackTraceLimit = Infinity;
require('es6-shim');
require('reflect-metadata');
require('ts-helpers');
require('zone.js/dist/zone');
require('http://ift.tt/2bzdqQw');
require('http://ift.tt/2bD0xlP');
require('http://ift.tt/2bzdzU8');
require('http://ift.tt/2bD0Rkt');

var appContext = require.context('./app', true, /\.spec\.ts/);
appContext.keys().forEach(appContext);

var testing = require('@angular/core/testing');
var browser = require('@angular/platform-browser-dynamic/testing');

testing.setBaseTestProviders(browser.TEST_BROWSER_DYNAMIC_PLATFORM_PROVIDERS, browser.TEST_BROWSER_DYNAMIC_APPLICATION_PROVIDERS);

Any idea what am i missing here? Help much appreciated.

Thanks