diff --git a/config/webpack.config.js b/config/webpack.config.js
index ffb161900933d5d1b1dc616c3020c9e2b5a69a40..ae92419054e23a62c8e7e1b51af3450b52d9776e 100644
--- a/config/webpack.config.js
+++ b/config/webpack.config.js
@@ -15,6 +15,9 @@ var DEV_SERVER_HOST = process.env.DEV_SERVER_HOST || 'localhost';
 var DEV_SERVER_PORT = parseInt(process.env.DEV_SERVER_PORT, 10) || 3808;
 var DEV_SERVER_LIVERELOAD = process.env.DEV_SERVER_LIVERELOAD !== 'false';
 var WEBPACK_REPORT = process.env.WEBPACK_REPORT;
+var babelLoader = 'babel-loader';
+
+if (!IS_PRODUCTION) babelLoader += '?plugins=rewire';
 
 var config = {
   context: path.join(ROOT_PATH, 'app/assets/javascripts'),
@@ -67,7 +70,7 @@ var config = {
       {
         test: /\.js$/,
         exclude: /(node_modules|vendor\/assets)/,
-        loader: 'babel-loader',
+        loader: babelLoader,
       },
       {
         test: /\.vue$/,
diff --git a/package.json b/package.json
index a17399ddb8f614b897e3d2af9a2e97849ccb97b3..953ea344f37705f3f5194465dd8fc86c5e4029e1 100644
--- a/package.json
+++ b/package.json
@@ -14,6 +14,7 @@
   "dependencies": {
     "babel-core": "^6.22.1",
     "babel-loader": "^6.2.10",
+    "babel-plugin-rewire": "^1.1.0",
     "babel-plugin-transform-define": "^1.2.0",
     "babel-preset-latest": "^6.24.0",
     "babel-preset-stage-2": "^6.22.0",
diff --git a/spec/javascripts/.eslintrc b/spec/javascripts/.eslintrc
index 3d922021978aac8315cbbd33dea2a7dc772a1062..a3a8bb050c95ea9b89034138697280b718a2cbbd 100644
--- a/spec/javascripts/.eslintrc
+++ b/spec/javascripts/.eslintrc
@@ -27,6 +27,19 @@
     "jasmine/no-suite-dupes": [1, "branch"],
     "jasmine/no-spec-dupes": [1, "branch"],
     "no-console": 0,
-    "prefer-arrow-callback": 0
+    "prefer-arrow-callback": 0,
+    "no-underscore-dangle": [
+      2,
+      {
+        "allow": [
+          "__GetDependency__",
+          "__Rewire__",
+          "__ResetDependency__",
+          "__get__",
+          "__set__",
+          "__RewireAPI__"
+        ]
+      }
+    ]
   }
 }
diff --git a/spec/javascripts/comment_type_toggle_spec.js b/spec/javascripts/comment_type_toggle_spec.js
index dfd0810d52e86cd299107087bda40d6339d2d328..2e7343aeb0d7adfbfda5fd6fe3c2c7e623d67f21 100644
--- a/spec/javascripts/comment_type_toggle_spec.js
+++ b/spec/javascripts/comment_type_toggle_spec.js
@@ -1,5 +1,4 @@
 import CommentTypeToggle from '~/comment_type_toggle';
-import * as dropLabSrc from '~/droplab/drop_lab';
 import InputSetter from '~/droplab/plugins/input_setter';
 
 describe('CommentTypeToggle', function () {
@@ -58,15 +57,16 @@ describe('CommentTypeToggle', function () {
       this.config = {};
 
       this.droplab = jasmine.createSpyObj('droplab', ['init']);
-
-      spyOn(dropLabSrc, 'default').and.returnValue(this.droplab);
+      this.DropLab = jasmine.createSpy('DropLab').and.returnValue(this.droplab);
       spyOn(this.commentTypeToggle, 'setConfig').and.returnValue(this.config);
 
+      CommentTypeToggle.__Rewire__('DropLab', this.DropLab);
+
       CommentTypeToggle.prototype.initDroplab.call(this.commentTypeToggle);
     });
 
     it('should instantiate a DropLab instance', function () {
-      expect(dropLabSrc.default).toHaveBeenCalled();
+      expect(this.DropLab).toHaveBeenCalled();
     });
 
     it('should set .droplab', function () {
@@ -77,7 +77,7 @@ describe('CommentTypeToggle', function () {
       expect(this.commentTypeToggle.setConfig).toHaveBeenCalled();
     });
 
-    it('should call DropLab.prototype.init', function () {
+    it('should call droplab.init', function () {
       expect(this.droplab.init).toHaveBeenCalledWith(
         this.commentTypeToggle.dropdownTrigger,
         this.commentTypeToggle.dropdownList,
diff --git a/spec/javascripts/droplab/hook_spec.js b/spec/javascripts/droplab/hook_spec.js
index 8ebdcdd1404f5760f735693ae55e054076ef15e5..e4625d7e2196fcd8d9b51160d3f94ddb74aac850 100644
--- a/spec/javascripts/droplab/hook_spec.js
+++ b/spec/javascripts/droplab/hook_spec.js
@@ -1,7 +1,6 @@
 /* eslint-disable */
 
 import Hook from '~/droplab/hook';
-import * as dropdownSrc from '~/droplab/drop_down';
 
 describe('Hook', function () {
   describe('class constructor', function () {
@@ -12,7 +11,8 @@ describe('Hook', function () {
       this.config = {};
       this.dropdown = {};
 
-      spyOn(dropdownSrc, 'default').and.returnValue(this.dropdown);
+      this.DropDown = jasmine.createSpy('DropDown').and.returnValue(this.dropdown);
+      Hook.__Rewire__('DropDown', this.DropDown);
 
       this.hook = new Hook(this.trigger, this.list, this.plugins, this.config);
     });
@@ -26,7 +26,7 @@ describe('Hook', function () {
     });
 
     it('should call DropDown constructor', function () {
-      expect(dropdownSrc.default).toHaveBeenCalledWith(this.list);
+      expect(this.DropDown).toHaveBeenCalledWith(this.list);
     });
 
     it('should set .type', function () {
diff --git a/yarn.lock b/yarn.lock
index e16cd9c36730167a9ef8534fd0e2a393be13c11d..6f8a397aabd7876e9a8e8d138f32af1956fa6ec5 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -425,6 +425,10 @@ babel-plugin-istanbul@^4.0.0:
     istanbul-lib-instrument "^1.4.2"
     test-exclude "^4.0.0"
 
+babel-plugin-rewire@^1.1.0:
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/babel-plugin-rewire/-/babel-plugin-rewire-1.1.0.tgz#a6b966d9d8c06c03d95dcda2eec4e2521519549b"
+
 babel-plugin-syntax-async-functions@^6.8.0:
   version "6.13.0"
   resolved "https://registry.yarnpkg.com/babel-plugin-syntax-async-functions/-/babel-plugin-syntax-async-functions-6.13.0.tgz#cad9cad1191b5ad634bf30ae0872391e0647be95"