unit-testing - 使用 Jest 测试 Vue3 组件时如何模拟计算属性

Question

情况

我正在尝试使用 Jest 测试一个简单的 Vue3 组件。我想评估某个文本是否被渲染。该决定取决于 bool 计算值 (isNeverShowAgain)，我想模拟该计算值。

<template>
    <div :class="{ modal: true, 'is-active': showDialog }">
    ....
                <WelcomeText />
    ....
    </div>
</template>
<script lang="ts">
    ....
export default defineComponent({
    name: 'WelcomeMessage',
    components: { WelcomeText },
    data() {
        return {
            /** Whether to show the message this time*/
            showDialog: false,
    ....
        };
    },
    beforeMount() {
        //Decide whether to actually show this dialog now, before mounting it, to avoid any flicker
        this.showDialog = !this.isNeverShowAgain === true;
    },
    ....
    computed: {
        /** Whether the welcome message has been permanently dismissed */
        isNeverShowAgain(): boolean {
            return this.$store.getters.neverShowWelcomeMessageAgain;
        },
    },
});
</script>

如上所示，在现实世界中，这个计算值 (isNeverShowAgain) 是从 vuex 存储属性中获取的，这就是我被卡住的地方。有很多帖子展示了如何模拟 vuex 存储，但这对我来说似乎太过分了。

问题

如何在不模拟整个 vuex 存储的情况下模拟 isNeverShowAgain 计算值？

上下文

这是我失败的测试:

/**
 * @jest-environment jsdom
 * @devdoc See https://github.com/vuejs/vue-test-utils-next/issues/194#issue-689186727 about the setup with "as any"
 */

import { mount } from '@vue/test-utils';
import WelcomeMessage from '@/components/WelcomeMessage.vue';

describe('WelcomeMessage.vue', () => {
    it('should display the message', () => {
        const wrapper = mount(WelcomeMessage, {
            computed: {
                isNeverShowAgain() {
                    return false;
                },
            },
        } as any);
        // wrapper.vm.setComputed({ isNeverShowAgain: false }); //Deprecated and does not work

        // Assert the rendered text of the component
        expect(wrapper.text()).toContain('Welcome');
    });
});

这是我得到的错误:

TypeError: Cannot read property 'getters' of undefined

  69 |         /** Whether the welcome message has been permanently dismissed */
  70 |         isNeverShowAgain(): boolean {
> 71 |             return this.$store.getters.neverShowWelcomeMessageAgain;
     |                                ^
  72 |         },
  73 |     },
  74 | });

很明显，问题出在未模拟的 vuex 存储上，但同样，我如何模拟计算值，这首先取决于存储？

注意事项

请记住，这是 Vue3 和匹配的 Jest2 测试工具，因此一些以前可用的功能现在已弃用，例如 setComputed。

我的依赖

"devDependencies": {
    .....
    "@types/jest": "^27.0.2",
    "@vue/test-utils": "^2.0.0-rc.16",
    "@vue/vue3-jest": "^27.0.0-alpha.3",
    "jest": "^27.3.1",
    "jest-cli": "^27.3.1",
    "ts-jest": "^27.0.7",
    "ts-node": "^10.4.0",
    "typescript": "~4.1.5",
},

Answer 1

你不必模拟计算，但你必须像这样模拟商店:

const wrapper = mount(WelcomeMessage, {
    $mocks: {
      $store: {
        getters: { 
           neverShowWelcomeMessageAgain: true
        }
      }    
    }
});