chore(karma): add coverage

Closes #4785

.gitignore

@@ -15,7 +15,7 @@ logs
 results
 dist
 # test coverage files
-coverage/
+.coverage/
 
 node_modules
 npm-debug.log

karma.conf.js

@@ -34,13 +34,19 @@ module.exports = function(config) {
     // preprocess matching files before serving them to the browser
     // available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
     preprocessors: {
+      'src/*/{*.js,!(test)/**/*.js}': ['coverage']
     },
 
 
     // test results reporter to use
     // possible values: 'dots', 'progress'
     // available reporters: https://npmjs.org/browse/keyword/karma-reporter
-    reporters: ['progress'],
+    reporters: ['progress', 'coverage'],
+
+    coverageReporter: {
+      dir: '.coverage/',
+      type: 'html'
+    },
 
     reportSlowerThan: 100,