How to unit test Vue.js components

Unit testing Vue.js components is an essential part of the development process to ensure the reliability and correctness of your code. Vue.js provides a testing utility called Vue Test Utils that makes it easy to write unit tests for your components. Here's a step-by-step guide on how to unit test Vue.js components:

1. Install Dependencies:

Ensure you have the necessary dependencies installed:

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npm install --save-dev @vue/test-utils jest @vue/cli-plugin-unit-jest

2. Configure Jest:

Update your package.json file to configure Jest for unit testing. Add the following section:

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"jest": {
  "moduleFileExtensions": [
    "js",
    "json",
    "vue"
  ],
  "transform": {
    "^.+\\.js$": "babel-jest",
    "^.+\\.vue$": "vue-jest"
  },
  "moduleNameMapper": {
    "^@/(.*)$": "<rootDir>/src/$1"
  },
  "snapshotSerializers": ["<rootDir>/node_modules/jest-serializer-vue"]
}

3. Write a Unit Test:

Create a test file for your component, for example, MyComponent.spec.js:

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

describe('MyComponent', () => {
  it('renders correctly', () => {
    const wrapper = mount(MyComponent)
    expect(wrapper.element).toMatchSnapshot()
  })

  it('handles user interaction', async () => {
    const wrapper = mount(MyComponent)
    await wrapper.setData({ value: 'Hello' })
    expect(wrapper.text()).toContain('Hello')
  })
})

4. Run Tests:

Add a script to your package.json to run the tests:

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"scripts": {
  "test:unit": "vue-cli-service test:unit"
}

Run the tests:

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npm run test:unit