mocha

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Original

English

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Translation

Chinese

Mocha

Mocha is a flexible JavaScript test framework. Unlike Jest, it does not come with an assertion library, mocking, or snapshotting built-in. It is a runner that allows you to choose your own tools (usually Chai + Sinon).

Mocha是一款灵活的JavaScript测试框架。与Jest不同，它不内置断言库、模拟或快照功能。它是一个测试运行器，允许你选择自己的工具（通常搭配Chai + Sinon）。

When to Use

适用场景

Flexibility: You want to pick your assertion library (Chai, Should.js).
Node.js Backends: standard in many Express/NestJS (legacy) setups.
Asynchronous Testing: Historically strong support for async (though standard now).

灵活性需求：你希望自行选择断言库（如Chai、Should.js）。
Node.js后端：在许多Express/NestJS（传统）项目中是标准配置。
异步测试：历来对异步操作支持出色（如今已成为通用特性）。

Quick Start

快速开始

javascript

// npm install --save-dev mocha chai
const assert = require("chai").assert;

describe("Array", function () {
  describe("#indexOf()", function () {
    it("should return -1 when the value is not present", function () {
      assert.equal([1, 2, 3].indexOf(4), -1);
    });
  });
});

javascript

// npm install --save-dev mocha chai
const assert = require("chai").assert;

describe("Array", function () {
  describe("#indexOf()", function () {
    it("should return -1 when the value is not present", function () {
      assert.equal([1, 2, 3].indexOf(4), -1);
    });
  });
});

Core Concepts

核心概念

BDD Interface

BDD接口

describe

(suite),

it

(test),

before

after

beforeEach

afterEach

describe

（测试套件）、

it

（测试用例）、

before

、

after

、

beforeEach

、

afterEach

。

Hooks

钩子函数

Mocha allows defining hooks at the root level or inside suites to set up/tear down environments.

Mocha允许在根级别或测试套件内定义钩子函数，用于环境的搭建与销毁。

Async support

异步支持

Use

async/await

in the

it

block callback.

javascript

it("should save user", async function () {
  const user = new User("tobi");
  await user.save();
});

在

it

块的回调函数中使用

async/await

。

javascript

it("should save user", async function () {
  const user = new User("tobi");
  await user.save();
});

Best Practices (2025)

2025年最佳实践

Do:

Use
.only
and
.skip
: Useful during development to run a single test (
```
it.only(...)
```
).
Use
nyc
(Istanbul): For code coverage (since Mocha doesn't have it built-in).

Don't:

Don't use arrow functions (
```
() => {}
```
) if you need
```
this.timeout()
```
or
```
this.slow()
```
. Mocha binds the test context to
```
this
```
.

建议:

使用
.only
和
.skip
: 开发期间可用于仅运行单个测试（
```
it.only(...)
```
）。
使用nyc（Istanbul）: 用于代码覆盖率统计（因为Mocha本身不内置该功能）。

不建议:

不要使用箭头函数 (
```
() => {}
```
)，如果你需要使用
```
this.timeout()
```
或
```
this.slow()
```
。Mocha会将测试上下文绑定到
```
this
```
上。

References

参考资料

Mocha Documentation

Mocha官方文档