Fix tests

Author: fzaninotto

.babelrc

@@ -1,10 +1,29 @@
 {
-  "presets": [
-    ["es2015", { "modules": false }],
-    "stage-0"
-  ],
-  "plugins": [
-    "external-helpers",
-    "transform-runtime"
-  ]
+  "env": {
+    "test": {
+      "presets": [
+        "es2015",
+        "stage-0"
+      ],
+      "plugins": [
+        "external-helpers",
+        "transform-runtime"
+      ]
+    },
+    "development": {
+      "presets": [
+        [
+          "es2015",
+          {
+            "modules": false
+          }
+        ],
+        "stage-0"
+      ],
+      "plugins": [
+        "external-helpers",
+        "transform-runtime"
+      ]
+    }
+  }
 }