add test coverage

.babelrc

@@ -1,3 +1,10 @@
 {
-  "presets": ["react-native"]
+  "presets": ["react-native"],
+  "env": {
+   "test": {
+     "plugins": [
+       "istanbul"
+     ]
+   }
+ }
 }

.gitignore

@@ -6,3 +6,5 @@
 #
 node_modules/
 npm-debug.log
+
+.nyc_output

package.json

@@ -4,8 +4,16 @@
   "description": "Cascading styles for ReactNative",
   "main": "src/index.js",
   "scripts": {
-    "test": "mocha --require tests/setup tests/*.spec.js",
-    "bench": "node -r babel-register bench/bench.js"
+    "test": "mocha --require test/setup test/*.spec.js",
+    "bench": "node -r babel-register bench/bench.js",
+    "cover": "cross-env NODE_ENV=test nyc mocha -r test/setup test/*.spec.js"
+  },
+  "nyc": {
+    "require": [
+      "babel-register"
+    ],
+    "sourceMap": false,
+    "instrument": false
   },
   "keywords": [
     "react-native",
@@ -24,10 +32,12 @@
   "license": "MIT",
   "devDependencies": {
     "babel-eslint": "^7.0.0",
+    "babel-plugin-istanbul": "^3.0.0",
     "babel-preset-react-native": "^1.9.0",
     "babel-register": "^6.18.0",
     "benchmark": "^2.1.2",
     "chai": "^3.5.0",
+    "cross-env": "^3.1.3",
     "enzyme": "^2.6.0",
     "eslint": "^3.3.1",
     "eslint-config-standard": "^6.2.1",
@@ -42,6 +52,7 @@
     "microtime": "^2.1.2",
     "mocha": "^3.2.0",
     "mocha-eslint": "^3.0.1",
+    "nyc": "^10.0.0",
     "react": "^15.4.1",
     "react-native": "^0.39.2",
     "react-native-mock": "^0.2.9"