Install and configure jest

1. We are using typescript in our project. To properly setup jest we would need to install ts-jest package as well.
   

   $ npm install --save-dev jest ts-jest @types/jest
   

2. git add -u

3. git commit -m 'install jest'

4. Initialize our ts-jest config.
   

   $ npx ts-jest config:init
   

5. Add test script in package.json
   

    "format": "prettier --write .",
   -    "lint": "eslint . --ext .js,.jsx,.ts,.tsx,.vue"
   +    "lint": "eslint . --ext .js,.jsx,.ts,.tsx,.vue",
   +    "test": "jest"
   

6. git add package.json jest.config.js

7. git commit -m 'add jest config'

Configure jest for vue

1. To make jest and vue work together, we will need vue-jest package. Recently it was split into vue2-jest and vue3-jest (we will use this one), which are currently in alpha. But we're still going to use it because this is the only version that supports jest >= 27.x. Also, for better testing experience with vue we will install @vue/test-utils -

   official testing utility library for Vue.js
   

   $ npm install --save-dev vue3-jest@27.0.0-alpha.2 @vue/test-utils@next
   

2. Update jest.config.js
   

      testEnvironment: 'node',
   +  transform: {
   +    '^.+\\.vue$': 'vue3-jest',
   +  },
   +  moduleFileExtensions: ['json', 'js', 'jsx', 'ts', 'tsx', 'vue']
   

3. git add -u

4. git commit -m 'install vue-jest and @vue/test-utils'

Add tests

1. mkdir -p tests/unit
2. touch tests/unit/HelloWorld.spec.ts

3. Add our test in tests/unit/HelloWorld.spec.ts
   

   +import { shallowMount } from '@vue/test-utils'
   +import HelloWorld from '@/components/HelloWorld.vue'
   +
   +describe('HelloWorld.vue', () => {
   +  it('renders props.msg when passed', () => {
   +    const msg = 'new message'
   +    const wrapper = shallowMount(HelloWorld, {
   +      props: { msg },
   +    })
   +    expect(wrapper.text()).toMatch(msg)
   +  })
   +})
   

4. git add -u

5. git commit -m 'add test'

6. Run test.
   

   $ npm run test
   

Fix error TS7016: Could not find a declaration file for module '@vue/test-utils'

1. If running tests causes this.
   

   $ npm run test
   
   > vite-vue-typescript-starter@0.0.0 test
   > jest
   
    FAIL  tests/unit/HelloWorld.spec.ts
     ● Test suite failed to run
   
       tests/unit/HelloWorld.spec.ts:1:30 - error TS7016: Could not find a declaration file for module '@vue/test-utils'. '/path/to/project/vue-ts/node_modules/@vue/test-utils/dist/vue-test-utils.cjs.js' implicitly has an 'any' type.
         Try `npm i --save-dev @types/vue__test-utils` if it exists or add a new declaration (.d.ts) file containing `declare module '@vue/test-utils';`
   
       1 import { shallowMount } from '@vue/test-utils'
                                      ~~~~~~~~~~~~~~~~~
   
   Test Suites: 1 failed, 1 total
   Tests:       0 total
   Snapshots:   0 total
   Time:        3.376 s
   Ran all test suites.
   

2. This is due to a bug in version 2.0.0-rc.11 which was fixed in 2.0.0-rc.12.

   • https://github.com/vuejs/vue-test-utils-next/releases/tag/v2.0.0-rc.12
   • https://github.com/vuejs/vue-test-utils-next/issues/799
   • https://github.com/vuejs/vue-test-utils-next/pull/800

3. Update to newer version of @vue/test-utils.
   

   $ npm install --save-dev @vue/test-utils@2.0.0-rc.12
   

4. git add -u

5. git commit -m 'fix: TS7016 missing declaration file for @vue/test-utils by updating it to 2.0.0-rc.12'

Fix Cannot find module '@/components/HelloWorld.vue' from 'tests/unit/HelloWorld.spec.ts'

1. If running tests causes.
   

   $ npm run test
   
   > vite-vue-typescript-starter@0.0.0 test
   > jest
   
    FAIL  tests/unit/HelloWorld.spec.ts
     ● Test suite failed to run
   
       Cannot find module '@/components/HelloWorld.vue' from 'tests/unit/HelloWorld.spec.ts'
   
         1 | import { shallowMount } from '@vue/test-utils'
       > 2 | import HelloWorld from '@/components/HelloWorld.vue'
           | ^
         3 |
         4 | describe('HelloWorld.vue', () => {
         5 |   it('renders props.msg when passed', () => {
   
         at Resolver.resolveModule (node_modules/jest-resolve/build/resolver.js:311:11)
         at Object.<anonymous> (tests/unit/HelloWorld.spec.ts:2:1)
   
   Test Suites: 1 failed, 1 total
   Tests:       0 total
   Snapshots:   0 total
   Time:        2.735 s
   Ran all test suites.
   

2. This issue occurs because jest cannot resolve @/ path.

   • https://kulshekhar.github.io/ts-jest/docs/getting-started/paths-mapping
   • https://jestjs.io/docs/configuration#modulenamemapper-objectstring-string--arraystring

3. Update jest.config.js to fix this.
   

   +  moduleNameMapper: {
   +    '^@/(.*)$': '<rootDir>/src/$1',
   +  },
   

4. git add -u

5. git commit -m "fix: jest can't find @/ path"

Fix ReferenceError: document is not defined

1. If running tests causes.
   

   $ npm run test
   
   > vite-vue-typescript-starter@0.0.0 test
   > jest
   
    FAIL  tests/unit/HelloWorld.spec.ts
     HelloWorld.vue
       ✕ renders props.msg when passed (2 ms)
   
     ● HelloWorld.vue › renders props.msg when passed
   
       The error below may be caused by using the wrong test environment, see https://jestjs.io/docs/configuration#testenvironment-string.
       Consider using the "jsdom" test environment.
   
       ReferenceError: document is not defined
   
          5 |   it('renders props.msg when passed', () => {
          6 |     const msg = 'new message'
       >  7 |     const wrapper = shallowMount(HelloWorld, {
            |                     ^
          8 |       props: { msg },
          9 |     })
         10 |     expect(wrapper.text()).toMatch(msg)
   
         at mount (node_modules/@vue/test-utils/dist/vue-test-utils.cjs.js:7640:14)
         at Object.shallowMount (node_modules/@vue/test-utils/dist/vue-test-utils.cjs.js:7852:12)
         at Object.<anonymous> (tests/unit/HelloWorld.spec.ts:7:21)
   
   Test Suites: 1 failed, 1 total
   Tests:       1 failed, 1 total
   Snapshots:   0 total
   Time:        4.061 s
   Ran all test suites.
   

2. As the error message suggests, we could fix this error by updating jest.config.js
   

   -  testEnvironment: 'node',
   +  testEnvironment: 'jsdom',
   

3. git add -u

4. git commit -m 'fix: using wrong env for jest'

Run tests in Github Actions

1. Rename bulid.yml to ci.yml to be more general on contents of this workflow.
   

   $ git mv .github/workflows/{build,ci}.yml
   

2. Update .github/workflow/ci.yml
   

   -name: Node.js CI
   +name: CI
   
    on:
      push:
   @@ -28,6 +28,7 @@ jobs:
              cache: 'npm'
          - run: npm ci
          - run: npm run build
   +      - run: npm run test
   

3. Update badge in README.md
   

   -![build](https://github.com/imomaliev/vue-ts/actions/workflows/build.yml/badge.svg)
   +![ci](https://github.com/imomaliev/vue-ts/actions/workflows/ci.yml/badge.svg)
   

4. git add -u

5. git commit -m 'setup github workflow to run tests'

Links

• https://jestjs.io
• https://kulshekhar.github.io/ts-jest/
• https://github.com/vuejs/vue-jest
• https://www.npmjs.com/package/vue3-jest
• https://next.vue-test-utils.vuejs.org/installation/
• https://github.com/lmiller1990/vtu-next-demo

Project