fix tests in droplab/hook_spec.js

spec/javascripts/droplab/hook_spec.js

 import Hook from '~/droplab/hook';
-import * as dropdownSrc from '~/droplab/drop_down';
 
 describe('Hook', function () {
   describe('class constructor', function () {
@@ -10,7 +9,7 @@ describe('Hook', function () {
       this.config = {};
       this.dropdown = {};
 
-      spyOn(dropdownSrc, 'default').and.returnValue(this.dropdown);
+      this.dropdownConstructor = spyOnDependency(Hook, 'DropDown').and.returnValue(this.dropdown);
 
       this.hook = new Hook(this.trigger, this.list, this.plugins, this.config);
     });
@@ -24,7 +23,7 @@ describe('Hook', function () {
     });
 
     it('should call DropDown constructor', function () {
-      expect(dropdownSrc.default).toHaveBeenCalledWith(this.list, this.config);
+      expect(this.dropdownConstructor).toHaveBeenCalledWith(this.list, this.config);
     });
 
     it('should set .type', function () {