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Mocha 复用测试用例

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Mocha 复用测试用例

发表于

2018-12-13

|

更新于 2019-05-10

| 分类于 Tutorial

| 评论数： 0

| 阅读次数：

在使用 Mocha 进行单元测试时，经常会有复用测试用例的需求。例如定义了一组测试用例后，希望在多种环境下都使用这组用例进行测试。

1. 测试环境

首先简单地搭建一个测试环境。

创建项目：

mkdir mocha-reuse
cd mocha-reuse
yarn init -y
yarn add -D mocha

项目目录结构如下：

  • index.js
  • test
    • index.test.js

其中 index.js 内容如下：

// index.js
module.exports = class Human {
  constructor(name, age) {
    if (typeof name === 'string') {
      this.name = name;
    } else if (name instanceof Buffer) {
      this.name = name.toString();
    } else {
      throw TypeError('Name can only be string or buffer');
    }
    if (typeof age === 'number') {
      this.age = age;
    } else if (typeof age === 'string') {
      this.age = Number(age);
    } else {
      throw TypeError('Age can only be number or string');
    }
  }
  toString() {
    return `${this.name}: ${this.age}`;
  }
}

逻辑非常简单，Human 类构造时需要两个参数，name 支持 string 和 Buffer；age 支持 number 和 string。

测试内容是，构造一个 Human 实例后测试 name、age 和 toString() 是否正确。

2. 无复用版本

为了提高测试覆盖率，必须使用每一种可能的参数组合实例化 Human。

// test/index.test.js
const assert = require('assert');
const Human = require('../index');

describe('Test with string name and number age', () => {
  let human;
  before(() => {
    human = new Human('A', 1);
  });
  it('Check name', () => {
    assert(human.name === 'A');
  });
  it('Check age', () => {
    assert(human.age === 1);
  });
  it('Check toString', () => {
    assert(human.toString() === 'A: 1');
  });
});

describe('Test with buffer name and number age', () => {
  let human;
  before(() => {
    human = new Human(Buffer.from('A'), 1);
  });
  it('Check name', () => {
    assert(human.name === 'A');
  });
  it('Check age', () => {
    assert(human.age === 1);
  });
  it('Check toString', () => {
    assert(human.toString() === 'A: 1');
  });
});

describe('Test with string name and string age', () => {
  let human;
  before(() => {
    human = new Human('A', '1');
  });
  it('Check name', () => {
    assert(human.name === 'A');
  });
  it('Check age', () => {
    assert(human.age === 1);
  });
  it('Check toString', () => {
    assert(human.toString() === 'A: 1');
  });
});

describe('Test with buffer name and string age', () => {
  let human;
  before(() => {
    human = new Human(Buffer.from('A'), '1');
  });
  it('Check name', () => {
    assert(human.name === 'A');
  });
  it('Check age', () => {
    assert(human.age === 1);
  });
  it('Check toString', () => {
    assert(human.toString() === 'A: 1');
  });
});

可以看到，除了初始化不同之外，所有的测试样例都是一样的，因此我们必须想办法复用测试用例

3. 复用测试用例

在 test 目录下创建新的文件 share.js，将复用的用例放在里面：

const assert = require('assert');

module.exports = function () {
  it('Check name', function () {
    assert(this.human.name === 'A');
  });
  it('Check age', function () {
    assert(this.human.age === 1);
  });
  it('Check toString', function () {
    assert(this.human.toString() === 'A: 1');
  });
};

此时目录结构变为：

  • index.js
  • test
    • index.test.js
    • share.js

index.test.js 变为：

const Human = require('../index');
const check = require('./share');

describe('Test with string name and number age', () => {
  before(function () {
    this.human = new Human('A', 1);
  });
  check();
});

describe('Test with buffer name and number age', () => {
  before(function () {
    this.human = new Human(Buffer.from('A'), 1);
  });
  check();
});

describe('Test with string name and string age', () => {
  before(function () {
    this.human = new Human('A', '1');
  });
  check();
});

describe('Test with buffer name and string age', () => {
  before(function () {
    this.human = new Human(Buffer.from('A'), '1');
  });
  check();
});

要注意的是，这里在所有涉及 this 的函数上，不要使用箭头函数。

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