使用vitest来模拟方法，通过单元测试vue组件。

MyComponent.vue

<script setup>
import { ref } from "vue";

const isSelectAll = ref(true);
const selectAllModel = ref(false);

const onChange = () => {
    isSelectAll.value = true;
    selectAllModel.value = false;
};
const onVisibleChange = () => {
  // do something than call
  onChange();
};
</script>

我想通过模拟onChange来单元测试onVisibleChange方法，并检查onChange是否被调用。

MyComponent.spec.js

import { mount } from 'vitest';
import { ref } from 'vue';
import MyComponent from './MyComponent.vue';

describe('MyComponent', () => {
  const wrapper = shallowMount(MyComponent);
  const spy = vi.spyOn(wrapper.vm, 'onChange');
  wrapper.vm.onVisibleChange();
  expect(spy).toHaveBeenCalled();
  expect(wrapper.vm.onChange).toHaveBeenCalled();
  // Both the expect gives error: AssertionError: expected "onChange" to be called at least once

  //Also tried
  const mock = vi.fn();
  wrapper.vm.onChange = mock;
  wrapper.vm.onVisibleChange();
  expect(mock).toHaveBeenCalled();   // AssertionError: expected "spy" to be called at least once
  expect(wrapper.vm.onChange).toHaveBeenCalled();  // TypeError: [Function onChange] is not a spy or a call to a spy!
})