Vue-Router simulation using Vue-Test-Utils and Vitest

Question

I'm trying to understand the logic of mocking Vue-Router with Vitest.

To do this, I tried setting up and simulating my test environment on a very simple project. When I try to follow the official documentation of Vue-Test-Utils, I always get an error. I don't know if it's because they use Jest.

Using a real vue-router solved my problem, but I think mocking a vue-router is better.

Below I will first convey the source code of the project, and then the errors I received.

Home.vue

<script setup lang="ts">
import {onMounted} from "vue";
import {useRoute} from "vue-router";

const route = useRoute()

onMounted(() => {
  console.log(route.query)
})
</script>

<template>
  <div>Home</div>
</template>

Home.spec.ts

import {expect, it, vi} from "vitest";
import {mount} from "@vue/test-utils";

import Home from "../src/components/Home.vue"

it('Home Test', async () => {
    const wrapper = mount(Home)

    expect(wrapper.exists()).toBeTruthy()
})

vite.config.ts

/// <reference types="vitest" />
import { defineConfig } from 'vite'
import vue from '@vitejs/plugin-vue'

// https://vitejs.dev/config/
export default defineConfig({
  plugins: [vue()],
  test: {
    environment: 'jsdom',
    include: ['./test/**/*.spec.ts'],
    exclude: ['node_modules', 'dist'],
    globals: true
  }
})

My error message is as follows: ..

What I tried

I tried to simulate vue-router like below

vi.mock('vue-router', () => ({
    useRoute: vi.fn(),
}))

Or just

vi.mock('vue-router')

This is my final Home.spec.ts file

import {expect, it, vi} from "vitest";
import {mount} from "@vue/test-utils";

import Home from "../src/components/Home.vue"

vi.mock('vue-router')

it('Home Test', async () => {
    const wrapper = mount(Home, {
        global: {
            stubs: ["router-link", "router-view"]
        }
    })

    expect(wrapper.exists()).toBeTruthy()
})

Answer 1

First, I want to see router-link or router-view in Home.vue:

<script setup lang="ts">
import { onMounted } from 'vue';
import { useRoute } from 'vue-router';

const route = useRoute();

onMounted(() => {
  console.log(route.query);
});
</script>

<template>
  <router-link to="home">Go to home</router-link>
  <router-view />
</template>

So, Home.spec.ts should look like this:

import { expect, it, vi } from 'vitest';
import { mount } from '@vue/test-utils';
import * as VueRouter from 'vue-router';
import Home from '../src/components/Home.vue';

describe('./path/to/Home.vue', () => {
  const useRouteSpy = vi.spyOn(VueRouter, 'useRoute');
  const getWrapper = () => mount(Home as any, {
    global: {
      stubs: {
        'router-link': { template: '<div/>' },
        'router-view': { template: '<div/>' },
      },
    },
  });

  it('the component should be mounted', () => {
    // ARRANGE
    const useRouteMock = useRouteSpy.mockImplementationOnce({ query: 'query' });
    // ACT
    const wrapper = getWrapper();
    // ASSERT
    expect(useRouteMock).toHaveBeenCalled();
    expect(wrapper.exists()).toBeTruthy();
  });
});

Some comments/suggestions:

• Use description to define test context
• Define a global function to mount components, reuse instead of duplication
• Use .spyOn() and .mockImplementation...() for monitoring and simulation
• Use some structured/direct way to write tests, such as AAA [arrange, act, assert] or GWT [given, when, then]. I've been testing it for a few years and still use it and it helps me understand what I'm testing
• Use .toHaveBeenCalled...() Check if the mock is working as expected
• mount() The stub in the function should be related to the component used in the template (so if you don't use it shouldn't be listed as a stub)

Hope it helps, cheers!