Added one basic unittest for component

front/test/unit/specs/components/common.spec.js

+import Username from '@/components/common/Username.vue'
+
+import { render } from '../../utils'
+
+describe('Username', () => {
+  it('displays username', () => {
+    const vm = render(Username, {username: 'Hello'})
+    expect(vm.$el.textContent).to.equal('Hello')
+  })
+})

front/test/unit/utils.js

 // helper for testing action with expected mutations
+import Vue from 'vue'
+
+export const render = (Component, propsData) => {
+  const Constructor = Vue.extend(Component)
+  return new Constructor({ propsData: propsData }).$mount()
+}
+
 export const testAction = ({action, payload, params, expectedMutations, expectedActions}, done) => {
   let mutationsCount = 0
   let actionsCount = 0