Jest - Javascript testing

最新推荐文章于 2024-01-30 16:21:33 发布

转载最新推荐文章于 2024-01-30 16:21:33 发布 · 266 阅读

0 ·

CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/THUDM/p/10061580.html

文章标签：

#javascript #json #ViewUI

本文详细介绍使用 Jest 进行 JavaScript 测试的方法，包括安装配置、编写测试用例、使用 expect 断言方法、设置前后置操作、描述块的使用、HTTP 请求测试以及模拟函数的应用。同时提供代码覆盖率报告的生成方法。

Jest - Javascript testing

2018-12-03 THUDM team Eunbi Choi

Getting Started

a. install jest

npm install --save-dev jest

b. edit package.json
```
{
  "scripts": {
    "test": "jest"
 }
}
```
c. write a test file named sum.test.js
```
test('adds 1 + 2 to equal 3', () => {
  expect(1+2).toBe(3);
});
```
d. run the test from command line

npm test --

API - Expect Methods

a. Value

// methods used frequently
expect(n).toBe();
expect(n).not.toBe();
expect(n).toEqual();
expect(n).toStrictEqual();
expect(n).toBeNull();
expect(n).toBeDefined();
expect(n).toBeUndefined();
expect(n).toBeTruthy();
expect(n).toBeFalsy();

b. Numbers

expect(value).toBeGreaterThan(3); expect(value).toBeGreaterThanOrEqual(3.5);
expect(value).toBeLessThan(5);
expect(value).toBeLessThanOrEqual(4.5);

c. Arrays

expect(shoppingList).toContain('beer');

d. Exceptions

expect(compileAndroidCode).toThrow();
expect(compileAndroidCode).toThrow(ConfigError);

e. Promises

expect(fetchData()).resolves.toBe('peanut butter');
expect(fetchData()).rejects.toMatch('error');

Complete method reference is here https://jestjs.io/docs/en/expect

Setup and Teardown

If you have some work you need to do repeatedly for many tests, you can use beforeEach and afterEach.

If you need to setup or teardown once, you can use beforeAll and afterAll.

beforeEach(() => {
  initializeCityDatabase();
});
afterEach(() => {
  clearCityDatabase();
});
beforeAll(() => {
  return initializeCityDatabase();
});
afterAll(() => {
  return clearCityDatabase();
});

Scoping - describe block

By default, the before and after blocks apply to every test in a file. You can also group tests together using a describe block. When they are inside a describe block, the before and afterblocks only apply to the tests within that describe block.

describe('matching cities to foods', () => {
  beforeEach(() => {
    return initializeFoodDatabase();
 });

  test('Vienna <3 sausage', () => {
    expect(isValidCityFoodPair('Vienna', 'WienerSchnitzel')).toBe(true);
 });

  test('San Juan <3 plantains', () => {
    expect(isValidCityFoodPair('San Juan', 'Mofongo')).toBe(true);
 });
});

Test Express.js with Supertest - test HTTP request

First of all, you need to install babel-cli, babel-preset-env, jest, supertest and superagent.

Test GET

const request = require('supertest');
const app = require('../app');

describe('Test GET /', () => {
    test('It should return 200 status code', () => {
        return request(app).get('/').then(res => {
            expect(res.statusCode).toBe(200);
       });
   });
});

Test POST

describe('Test GET /', () => {
    test('It should return some res', (done) => {
        return request(app)
           .post('/wechat?open_id=abc')
           .type('xml')
           .send('<xml>' +
                  '<ToUserName>testuser</ToUserName>' +
                  '<FromUserName>testuser</FromUserName>' +
                  '<CreateTime>1348831860</CreateTime>' +
                  '<MsgType>text</MsgType>' +
                  '<Content>testcontent</Content>' +
                  '<MsgId>1234567890</MsgId>' +
                  '</xml>');
           })
           .then(res => {
                setTimeout(() => {
                expect(res.text).toMatch('some res');
                done();
               }, 500);
           });

       });
   });
});

Mock function

Mock functions make it easy to test the links between code by erasing the actual implementation of a function, capturing calls to the function (and the parameters passed in those calls), capturing instances of constructor functions when instantiated with new, and allowing test-time configuration of return values.

jest.fn([implementation]) return a new, unused mock function.

I used mock function to record all log strings in a string instead of printing it on command line. Below example is mocking console.log.
```
let log_output = "";
const storeLog = input => (log_output += input);

test('It should save all log strings in log_output', () => {
    console.log = jest.fn(storeLog); // mock function
    execute_some_func()
       .then(() => {
        expect(log_output).toMatch('Success');
    });
});
```
Built-in code coverage reports

The jest command line runner has a number of useful options. Below is one useful option coverage.

--coverage: Indicates that test coverage information should be collected and reported in the output.

We can easily create code coverage reports using --coverage. No additional setup or libraries needed! Jest can collect code coverage information from entire projects, including untested files.
Reference
- https://jestjs.io/en/
- How to test Express.js with Jest and Supertest

转载于:https://www.cnblogs.com/THUDM/p/10061580.html