Fix babelrc for tests

.babelrc

@@ -1,11 +1,3 @@
 {
-  "presets":[
-    ["env", {
-      modules: false,
-      targets: {
-        browsers: ['> 1%']
-      }
-    }]
-  ],
-  "plugins": ["transform-export-extensions", "external-helpers"],
+  "presets": ["./babel/config"]
 }

babel/config.js

@@ -0,0 +1,21 @@
+const envPreset = require('babel-preset-env').default;
+
+const testing = process.env.BABEL_ENV === 'test';
+
+const plugins = ['transform-export-extensions'];
+
+if (!testing) {
+  plugins.push('external-helpers');
+}
+
+module.exports = {
+  presets:[
+    ['env', {
+      modules: testing ? 'commonjs' : false,
+      targets: {
+        browsers: ['> 1%']
+      }
+    }]
+  ],
+  plugins: plugins
+};

package.json

@@ -13,7 +13,7 @@
     "prebuild": "rimraf dist",
     "build": "node ./scripts/build",
     "prepublishOnly": "in-publish && npm run build",
-    "test": "jest"
+    "test": "cross-env BABEL_ENV=test jest"
   },
   "repository": {
     "type": "git",
@@ -40,6 +40,7 @@
     "babel-plugin-external-helpers": "^6.22.0",
     "babel-plugin-transform-export-extensions": "^6.22.0",
     "babel-preset-env": "^1.5.2",
+    "cross-env": "^5.0.1",
     "gzip-size": "^3.0.0",
     "in-publish": "^2.0.0",
     "jest": "^20.0.4",