Unit Testing in Vue: A Comprehensive Guide
Writing unit tests is a crucial step in building robust and high-quality software. In this article, we’ll explore the importance of unit testing in Vue.js applications and provide a comprehensive guide on how to write unit tests using Avoriaz, a testing utility library for Vue.js.
Setting Up the Environment
To get started, we’ll use the Vue CLI to create a new project. If you don’t have the Vue CLI installed, you can install it by running the following command:
bash
npm install -g vue-cli
Next, create a new project using the following command:
bash
vue init webpack my-project
Follow the prompts to set up your project, making sure to select the option to include Vuex and unit tests with Karma and Mocha.
Understanding the Default Test
Let’s take a look at the default test file test/unit/specs/Hello.spec.js. This file contains a simple test that checks if the Hello component renders correctly.
“`javascript
import Vue from ‘vue’
import Hello from ‘@/components/Hello’
describe(‘Hello.vue’, () => {
it(‘should render correct content’, () => {
const vm = new Vue(Hello).$mount()
expect(vm.$el.querySelector(‘.hello h1’).textContent).toBe(‘Welcome to Your Vue.js App’)
})
})
“`
This test imports the Vue library and the Hello component, then uses the describe function to define a test suite. The it function is used to define a single test, which checks if the Hello component renders the correct content.
Writing Vue Tests with Avoriaz
Avoriaz is a testing utility library that provides a simpler way to write unit tests for Vue.js applications. To use Avoriaz, we need to install it first:
bash
npm install --save-dev avoriaz
Next, let’s rewrite the default test using Avoriaz:
“`javascript
import { mount } from ‘avoriaz’
import Hello from ‘@/components/Hello’
describe(‘Hello.vue’, () => {
it(‘should render correct content’, () => {
const wrapper = mount(Hello)
expect(wrapper.text()).toBe(‘Welcome to Your Vue.js App’)
})
})
“`
In this example, we import the mount function from Avoriaz and use it to render the Hello component. We then use the text method to check if the component renders the correct content.
Creating a Testable Component
Let’s create a new component called Happy that we can test:
“`javascript
// src/components/Happy.vue
{{ item }}
“`
This component has a getThem method that simulates an async call and adds a new item to the items array.
Testing the Happy Component
Let’s write a test for the Happy component:
“`javascript
import { mount } from ‘avoriaz’
import Happy from ‘@/components/Happy’
describe(‘Happy.vue’, () => {
it(‘should render correct content’, () => {
const wrapper = mount(Happy)
expect(wrapper.text()).toBe(‘Happy New Year’)
})
it(‘should add new item after async call’, (done) => {
const wrapper = mount(Happy)
wrapper.vm.getThem()
setTimeout(() => {
expect(wrapper.text()).toBe(‘Happy New Year Async Item’)
done()
}, 1000)
})
})
“`
In this example, we use the mount function to render the Happy component and then use the text method to check if the component renders the correct content. We also test the getThem method by simulating an async call and checking if the new item is added to the items array.
Conclusion
Writing unit tests is an essential part of building robust and high-quality software. In this article, we’ve explored the importance of unit testing in Vue.js applications and provided a comprehensive guide on how to write unit tests using Avoriaz. By following these best practices, you can ensure that your Vue.js applications are reliable, maintainable, and scalable.