Code coverage for unit tests

.babelrc

@@ -0,0 +1,16 @@
+{
+  "env": {
+    "test": {
+      "plugins": [
+        [
+          "istanbul",
+          {
+            "exclude": [
+              "test/**/*.js"
+            ]
+          }
+        ]
+      ]
+    }
+  }
+}

.gitignore

@@ -1,3 +1,4 @@
 dist/*
 node_modules/
 .env
+test/coverage

karma.conf.js

@@ -1,6 +1,6 @@
 /* eslint-env node */
 
-const reporters = ["mocha", "coverage"];
+const reporters = ["mocha", "istanbul"];
 if (process.env.COVERALLS_REPO_TOKEN) {
   reporters.push("coveralls");
 }
@@ -16,7 +16,7 @@ module.exports = function(config) {
     ],
     frameworks: ["mocha", "chai"],
     reporters,
-    coverageReporter: {
+    istanbulReporter: {
       dir: "test/coverage",
       reporters: [
         {
@@ -25,13 +25,10 @@ module.exports = function(config) {
         },
         {
           type: "html",
-          subdir(browser) {
-            // normalization process to keep a consistent browser name
-            // across different OS
-            return browser.toLowerCase().split(/[ /-]/)[0];
-          },
         },
-        { type: "text-summary" },
+        {
+          type: "text-summary",
+        },
       ],
     },
     files: [
@@ -40,11 +37,12 @@ module.exports = function(config) {
       "src/feature.js",
       "test/unit/*.spec.js",
     ],
-    // preprocessors: { "src/feature.js": ["coverage"] },
+    preprocessors: { "src/feature.js": ["babel"] },
     plugins: [
+      "karma-babel-preprocessor",
       "karma-chai",
       "karma-coveralls",
-      "karma-coverage",
+      "karma-istanbuljs-reporter",
       "karma-firefox-launcher",
       "karma-mocha",
       "karma-mocha-reporter",

package.json

@@ -10,6 +10,9 @@
     "shield-studies-addon-utils": "github:mozilla/shield-studies-addon-utils#develop"
   },
   "devDependencies": {
+    "babel-core": "^6.26.3",
+    "babel-plugin-istanbul": "^4.1.6",
+    "babel-preset-env": "^1.7.0",
     "chai": "^4.1.2",
     "doctoc": "^1.3.0",
     "eslint": "^4.7.2",
@@ -26,10 +29,12 @@
     "istanbul": "^1.1.0-alpha.1",
     "jshint": "^2.9.5",
     "karma": "^1.7.1",
+    "karma-babel-preprocessor": "^7.0.0",
     "karma-chai": "^0.1.0",
     "karma-coverage": "^1.1.2",
     "karma-coveralls": "^1.1.2",
     "karma-firefox-launcher": "^1.0.1",
+    "karma-istanbuljs-reporter": "^0.2.0",
     "karma-mocha": "^1.3.0",
     "karma-mocha-reporter": "^2.2.4",
     "minimist": "^1.2.0",