message: fix v-on unit test
diff: import Vue from 'vue'
  describe('Directive v-on', () => {
  - let vm, spy, spy2, el
  + let vm, spy, el
  beforeEach(() => {
  spy = jasmine.createSpy()
  - spy2 = jasmine.createSpy()
  el = document.createElement('div')
  document.body.appendChild(el)
  })
  @@ -88,12 +87,15 @@ describe('Directive v-on', () => {
  template: `
  <input type="checkbox" ref="input" @click.prevent="foo">
  `,
  - methods: { foo: spy2 }
  + methods: {
  + foo ($event) {
  + spy($event.defaultPrevented)
  + }
  + }
  })
  vm.$refs.input.checked = false
  triggerEvent(vm.$refs.input, 'click')
  - expect(spy2).toHaveBeenCalled()
  - expect(vm.$refs.input.checked).toBe(false)
  + expect(spy).toHaveBeenCalledWith(true)
  })
  it('should support capture', () => {
  