Support coverage with instabul and nyc

.babelrc

@@ -1,4 +1,11 @@
 {
   "presets": ["env"],
-  "plugins": ["babel-plugin-add-module-exports"]
-}
+  "plugins": ["babel-plugin-add-module-exports"],
+  "env": {
+    "test": {
+      "plugins": [
+        ["istanbul"]
+      ]
+    }
+  }
+}

.gitignore

@@ -12,6 +12,7 @@ lib-cov
 
 # Coverage directory used by tools like istanbul
 coverage
+.nyc_output
 
 # Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
 .grunt

package.json

@@ -7,7 +7,8 @@
     "build": "webpack --env dev && webpack --env build && npm run test",
     "dev": "webpack --progress --colors --watch --env dev",
     "test": "mocha --require babel-register --colors ./test/*.spec.js",
-    "test:watch": "mocha --require babel-register --colors -w ./test/*.spec.js"
+    "test:watch": "mocha --require babel-register --colors -w ./test/*.spec.js",
+    "test:cover": "cross-env NODE_ENV=test nyc mocha --require babel-register --colors test/*.js"
   },
   "repository": {
     "type": "git",
@@ -35,9 +36,11 @@
     "babel-eslint": "^8.0.3",
     "babel-loader": "^8.0.0-beta.4",
     "babel-plugin-add-module-exports": "^0.2.1",
+    "babel-plugin-istanbul": "^5.1.0",
     "babel-preset-env": "^7.0.0-beta.3",
     "babel-register": "^7.0.0-beta.3",
     "chai": "^4.1.2",
+    "cross-env": "^5.2.0",
     "eslint": "^5.0.1",
     "eslint-loader": "^2.0.0",
     "jsdom": "11.11.0",
@@ -47,5 +50,12 @@
     "webpack": "^4.12.2",
     "webpack-cli": "^3.0.8",
     "yargs": "^10.0.3"
+  },
+  "dependencies": {
+    "nyc": "^13.1.0"
+  },
+  "nyc": {
+    "sourceMap": false,
+    "instrument": false
   }
 }

webpack.config.js

@@ -20,7 +20,7 @@ if (env === 'build') {
 const config = {
   mode: mode,
   entry: __dirname + '/src/index.js',
-  devtool: 'source-map',
+  devtool: 'inline-source-map',
   output: {
     path: __dirname + '/lib',
     filename: outputFile,