How do you test Vue components that use Vuex, Vue Router, or other plugins?

1 What is TDD?

TDD is a software development approach that involves writing tests before writing the actual code. The idea is to specify the expected behavior and functionality of your code with tests, and then write the code that makes the tests pass. This way, you can avoid bugs, refactor your code with confidence, and design your code with clarity and simplicity.

2 How to set up a testing environment for Vue?

To test your Vue components, you need a testing environment that can run your tests and simulate the browser. There are several tools and libraries that can help you with this, such as Jest, Mocha, Chai, Vue Test Utils, and Vue Testing Library. You can choose the ones that suit your preferences and needs, but in this article, we will use Jest as the test runner and Vue Testing Library as the testing utility.

3 How to test components that use Vuex?

Vuex is a state management library that helps you manage the data and logic of your application. To test components that use Vuex, you need to create a mock store that mimics the behavior of your real store. You can use the createLocalVue function from Vue Test Utils to create a local Vue instance that has Vuex installed, and then pass a mock store object to the localVue option when mounting your component. Alternatively, you can use the provide option to inject the mock store directly into your component.

5 How to test components that use other plugins?

Besides Vuex and Vue Router, there are many other plugins that can enhance the functionality and features of your Vue application, such as Axios, Vuetify, or Vue Apollo. To test components that use other plugins, you need to mock the plugins or their dependencies so that they do not interfere with your tests. You can use the createLocalVue function from Vue Test Utils to create a local Vue instance that has the plugins installed, and then use the jest.mock function to mock the modules or functions that the plugins use.

6 How to write tests with TDD?

Now that you know how to set up your testing environment and mock your plugins, you can start writing tests with TDD. The process involves writing a failing test that describes a feature or requirement of your component, then writing the minimum amount of code to make it pass. After refactoring your code to improve its quality and readability, you repeat the cycle until all features and requirements are covered. You can use Jest's describe, it, and expect functions to write the tests, and the render, fireEvent, and waitFor functions from Vue Testing Library to interact with your component. Additionally, you can access elements of your component by their roles, labels, or texts using the screen object from Vue Testing Library.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?