How to mock vue mixins during unit testing using vue

#How to mock vue mixins during unit testing using vue| 来源: 网络整理| 查看: 265

Unit testing is an important aspect of software development, as it helps to ensure that individual parts of an application work as intended. Vue.js applications can be unit tested using vue-test-utils and jest, which provide a suite of utilities for testing Vue components. When writing tests for Vue components, it's often necessary to mock mixins in order to isolate the component under test and control its behavior. Mocking mixins can be tricky, however, and requires careful attention to the details of your test setup. In this answer, we will discuss several methods for mocking mixins during unit testing of Vue components using vue-test-utils and jest.

Method 1: Mocking Mixins Globally

Mocking Vue mixins is an essential part of unit testing in Vue.js applications. Vue-test-utils and Jest provide various methods to mock mixins during unit testing. In this tutorial, we will learn how to mock Vue mixins globally using vue-test-utils and Jest.

Step 1: Create a mock mixin

To mock a Vue mixin, we need to create a mock mixin that returns the desired values. Here is an example of a mock mixin:

const mockMixin = { data() { return { mockData: 'mock data' } }, methods: { mockMethod() { return 'mock method' } } }

This mock mixin has a data property that returns a mock data value and a methods property that returns a mock method.

Step 2: Register the mock mixin globally

To register the mock mixin globally, we need to use the Vue.mixin method. Here is an example of how to register the mock mixin globally:

import Vue from 'vue' const mockMixin = { data() { return { mockData: 'mock data' } }, methods: { mockMethod() { return 'mock method' } } } Vue.mixin(mockMixin)

This code registers the mockMixin globally, so it will be available in all Vue components.

Step 3: Use the mock mixin in unit tests

To use the mock mixin in unit tests, we need to import the Vue component that uses the mixin and mount it using vue-test-utils. Here is an example of how to use the mock mixin in a unit test:

import { mount } from '@vue/test-utils' import MyComponent from './MyComponent.vue' describe('MyComponent', () => { it('renders with mock data', () => { const wrapper = mount(MyComponent) expect(wrapper.vm.mockData).toBe('mock data') }) it('calls mock method', () => { const wrapper = mount(MyComponent) expect(wrapper.vm.mockMethod()).toBe('mock method') }) })

This code mounts the MyComponent and tests that the mock data and mock method are available in the component.

That's it! This is how you can mock Vue mixins globally using vue-test-utils and Jest. By following these steps, you can easily mock any Vue mixin and test your components with confidence.

Method 2: Mocking Mixins Locally in the Component Under Test

To mock Vue Mixins during unit testing using vue-test-utils and jest, you can use the "Mocking Mixins Locally in the Component Under Test" approach. This approach involves mocking the mixin directly in the component being tested.

Here is an example of how to mock a mixin locally in a component:

import { shallowMount } from '@vue/test-utils' import MyComponent from '@/components/MyComponent.vue' describe('MyComponent', () => { it('renders correctly', () => { const wrapper = shallowMount(MyComponent, { mixins: [{ created() { console.log('Mixin created') } }] }) expect(wrapper.html()).toMatchSnapshot() }) })

In this example, we are mocking a mixin that adds a created hook to the component. We pass the mixin to the shallowMount function using the mixins option.

We can then test that the mixin has been applied by checking for the console log message in the test output.

import { shallowMount } from '@vue/test-utils' import MyComponent from '@/components/MyComponent.vue' describe('MyComponent', () => { it('calls mixin created hook', () => { const mixin = { created() { console.log('Mixin created') } } const wrapper = shallowMount(MyComponent, { mixins: [mixin] }) expect(mixin.created).toHaveBeenCalled() }) })

In this example, we are testing that the created hook in the mixin has been called. We define the mixin as a separate object and pass it to the shallowMount function. We then use the toHaveBeenCalled matcher to check that the created hook has been called.

By mocking mixins locally in the component under test, we can easily test the behavior of mixins in isolation.

Method 3: Using the jest.mock Function to Control Mixin Behavior

To mock Vue mixins during unit testing using vue-test-utils and jest, you can use the jest.mock function to control mixin behavior. Here are the steps to do it:

Import the mixin and the component to be tested: import MyMixin from '@/mixins/MyMixin' import MyComponent from '@/components/MyComponent' Mock the mixin using the jest.mock function: jest.mock('@/mixins/MyMixin', () => ({ myMixinMethod: jest.fn() })) Create a wrapper for the component and pass the mocked mixin: const wrapper = mount(MyComponent, { mixins: [MyMixin] }) Test the component and assert that the mocked mixin method was called: it('calls myMixinMethod', () => { expect(MyMixin.myMixinMethod).toHaveBeenCalled() })

Here's the complete code example:

import { mount } from '@vue/test-utils' import MyMixin from '@/mixins/MyMixin' import MyComponent from '@/components/MyComponent' jest.mock('@/mixins/MyMixin', () => ({ myMixinMethod: jest.fn() })) describe('MyComponent', () => { it('calls myMixinMethod', () => { const wrapper = mount(MyComponent, { mixins: [MyMixin] }) expect(MyMixin.myMixinMethod).toHaveBeenCalled() }) })

In this example, the MyMixin is mocked using the jest.mock function, and then passed as a mixin to the MyComponent being tested. The test then asserts that the mocked myMixinMethod was called.

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