# Jest Axios
# Introduction
Jest Axios is a Jest plugin that simplifies the process of mocking axios requests during testing. It fully utilizes Jest's built-in capabilities for mocking functions, and will automatically override requests made using axios throughout your application.
It does this with three main features:
- Easy configuration for defining functions to return data for specific endpoints and request methods.
- An internal database for storing data to serve via endpoint mocks.
- Providing tools that minimize boilerplate when mocking data for data models and collections of models.
# Why is this Useful?
It can be difficult to test JavaScript packages and complex web applications that fetch data from external services. Jest provides good tools for mocking data, but those tools aren't scalable for axios specifically or easy to configure for common REST API patterns. The result is a lot of unnecessary boilerplate in Jest tests, which can cause confusion and increase the maintenance burden of a test suite. This package simplifies that process by providing users a tool to quickly and robustly spin up mocked API services that will serve real data when axios requests are made throughout an application.
# Prerequisites
This documentation assumes users have at least a practical understanding of ES6 syntax and constructs. This documentation has code examples heavily utilizing ES6 constructs.
# Quickstart
The documentation that follows details how to mock a REST API for a minimal todo list application. First, we'll define configuration for mocking requests in our application, and will then use axios in jest tests to showcase the mocked requests.
For more detailed documentation about how to define and configure mock REST API services with this library, see the Guide section of the documentation.
To start, here is the syntax for configuring a server to mock requests:
// contents of tests/index.test.js
import axios from 'axios';
import { Server } from 'jest-axios';
class App extends Server {
data() {
return {
todos: [
{ name: 'foo', done: false },
{ name: 'bar', done: true },
],
};
}
api() {
return {
'/todos': this.collection('todos'),
'/todos/:id': this.model('todos'),
'/todos/:id/complete': {
post: id => this.db.todos.update(id, { done: true });
},
};
}
}
Once we have this defined, we need to configure our tests to initialize the server and mock axios:
// contents of tests/index.test.js
...
server = App('todo-app');
jest.mock('axios');
server.init(axios);
With the server initialized, let's run some tests to show the mocked requests:
// contesnts of tests/index.test.js
...
test('api.test', async () => {
// issue request
const response = await axios.get('/todos');
// check status code
assert.equal(response.status, 200);
// check payload
assert.equal(response.data, [
{ id: 1, name: 'foo', done: false },
{ id: 2, name: 'bar', done: true },
]);
// issue missing request and check error
try {
await axios.get('/missing');
assert.fail('Endpoint `/missing` should have returned error.');
} catch (err) {
assert.equal(err.status, 404);
}
// get specific todo item
let todo = await axios.get('/todos/1').then(response => response.data);
assert.equal(todo, { name: 'foo', done: false });
// complete todo item and check again
await axios.post('/todos/1/complete');
todo = await axios.get('/todos/1').then(response => response.data);
assert.equal(todo.done, true);
});
That's it! This library will also automatically mock any axios requests you make throughout your project, so you don't need to directly make axios calls inside tests to benefit from this package.
This simple example showcases only a small portion of the features available in the package. For more detailed examples and explanations, see the Usage section of the documentation.
For API documentation, see the API section of the documentation.