function sum(a, b) {
  return a + b;
}
module.exports = sum;
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const { expect, assert } = require('chai');
const sum = require('../sum');
describe('sum', function() {
  it('adds 1 + 2 to equal 3', () => {
    assert(sum(1, 2) === 3);
  });
});
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const sum = require('./sum');
describe('sum function test', () => {
  it('sum(1, 2) === 3', () => {
    expect(sum(1, 2)).toBe(3);
  });

  // 这里 test 和 it 没有明显区别，it 是指: it should xxx, test 是指 test xxx
  test('sum(1, 2) === 3', () => {
    expect(sum(1, 2)).toBe(3);
  });
})
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npm install --save-dev jest
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function sum(a, b) {

  return a + b;

}

module.exports = sum;
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const sum = require('../sum');
test('adds 1 + 2 to equal 3', () => {
  expect(sum(1, 2)).toBe(3);
});
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{
  "scripts": {
    "test": "jest"
  },
}
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export function sum(a, b) {
  return a + b;
}
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import { sum } from '../sum';
test('adds 1 + 2 to equal 3', () => {
  expect(sum(1, 2)).toBe(3);
});
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npm install --save-dev @babel/core @babel/preset-env
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{   "presets": ["@babel/preset-env"] }
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npm install --save-dev @babel/preset-typescript
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{   "presets": ["@babel/preset-env", "@babel/preset-typescript"] }
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npm install --save-dev @types/jest
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/**
 * 访问嵌套对象，避免代码中出现类似 user && user.personalInfo ? user.personalInfo.name : null 的代码
 */
export function get<T>(object: any, path: Array<number | string>, defaultValue?: T) : T {
  const result = path.reduce((obj, key) => obj !== undefined ? obj[key] : undefined, object);
  return result !== undefined ? result : defaultValue;
}
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import { get } from './get';
test('测试嵌套对象存在的可枚举属性 line1', () => {
  expect(get({
    id: 101,
    email: 'jack@dev.com',
    personalInfo: {
      name: 'Jack',
      address: {
        line1: 'westwish st',
        line2: 'washmasher',
        city: 'wallas',
        state: 'WX'
      }
    }
  }, ['personalInfo', 'address', 'line1'])).toBe('westwish st');
});
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"scripts": {     "test": "jest --watchAll"   },
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单元测试覆盖率 = 被测代码行数 / 参测代码总行数 * 100%
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module.exports = {
  // 是否显示覆盖率报告
  collectCoverage: true,
  // 告诉 jest 哪些文件需要经过单元测试测试
  collectCoverageFrom: ['get.ts', 'sum.ts', 'src/utils/**/*'],
}
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module.exports = {
  collectCoverage: true, // 是否显示覆盖率报告
  collectCoverageFrom: ['get.ts', 'sum.ts', 'src/utils/**/*'], // 告诉 jest 哪些文件需要经过单元测试测试
  coverageThreshold: {
    global: {
      statements: 90, // 保证每个语句都执行了
      functions: 90, // 保证每个函数都调用了
      branches: 90, // 保证每个 if 等分支代码都执行了
    },
  },
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/**
 * 环境参数枚举
 */
 enum IEnvEnum {
  DEV = 'dev', // 开发
  TEST = 'test', // 测试
  PRE = 'pre', // 预发
  PROD = 'prod', // 生产
}
/**
 * 根据链接获取当前环境参数
 * @param {string?} url 资源链接
 * @returns {IEnvEnum} 环境参数
 */
export function fetchEnv(url: string): IEnvEnum {
  const envs = [IEnvEnum.DEV, IEnvEnum.TEST, IEnvEnum.PRE];
  return envs.find((env) => url.includes(env)) || IEnvEnum.PROD;
}
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import { fetchEnv } from '../src/utils/fetchEnv';
describe('fetchEnv', () => {
  it ('判断是否 dev 环境', () => {
    expect(fetchEnv('https://www.imooc.dev.com/')).toBe('dev');
  });
  it ('判断是否 test 环境', () => {
    expect(fetchEnv('https://www.imooc.test.com/')).toBe('test');
  });
  it ('判断是否 pre 环境', () => {
    expect(fetchEnv('https://www.imooc.pre.com/')).toBe('pre');
  });
  it ('判断是否 prod 环境', () => {
    expect(fetchEnv('https://www.imooc.prod.com/')).toBe('prod');
  });
  it ('判断是否 prod 环境', () => {
    expect(fetchEnv('https://www.imooc.com/')).toBe('prod');
  });
});
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import { sum } from './sum';
test('sum(2, 4) 不等于 5', () => {
  expect(sum(2, 4)).not.toBe(5);
})
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export const getUserInfo = () => {
  return {
    name: 'moji',
    age: 24,
  }
}
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import { getUserInfo }  from '../src/userInfo.js';
test('getUserInfo()返回的对象深度相等', () => {
  expect(getUserInfo()).toEqual(getUserInfo());
})
test('getUserInfo()返回的对象内存地址不同', () => {
  expect(getUserInfo()).not.toBe(getUserInfo());
})
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export const getIntArray = (num) => {
  if (!Number.isInteger(num)) {
    throw Error('"getIntArray"只接受整数类型的参数');
  }
  return [...new Array(num).keys()];
};
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./test/getIntArray.test.js
import { getIntArray }  from '../src/utils/getIntArray';
test('getIntArray(3)返回的数组长度应该为3', () => {
  expect(getIntArray(3)).toHaveLength(3);
})
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import { getIntArray }  from '../src/utils/getIntArray';
test('getIntArray(3.3)应该抛出错误', () => {
  function getIntArrayWrapFn() {
    getIntArray(3.3);
  }
  expect(getIntArrayWrapFn).toThrow('"getIntArray"只接受整数类型的参数');
})
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import { getUserInfo }  from '../src/utils/userInfo.js';
test("getUserInfo().name 应该包含'mo'", () => {
  expect(getUserInfo().name).toMatch(/mo/i);
})
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/**  
 * 获取用户信息
*/
export const fetchUser = () => {
  return new Promise((resole) => {
    setTimeout(() => {
      resole({
        name: 'moji',
        age: 24,
      })
    }, 2000)
  })
}
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import { fetchUser } from '../src/fetchUser';
test('fetchUser() 可以请求到一个用户名字为 moji', async () => {
  const data =  await fetchUser();
  expect(data.name).toBe('moji')
})
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npm install --save-dev @babel/plugin-transform-runtime
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{
  "presets": ["@babel/preset-env", "@babel/preset-typescript"],
  "plugins": ["@babel/plugin-transform-runtime"]
}
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const names = ['liam', 'jim', 'bart'];
test('匹配对象是否包含', () => {
  expect(names).toContain('jim');
})
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toBeNull 仅匹配 null
toBeUndefined 仅匹配 undefined
toBeDefined 与…相反 toBeUndefined
toBeTruthy 匹配 if 语句视为 true 的任何内容
toBeFalsy 匹配 if 语句视为 false 的任何内容
检查数字类型（number）
toBeGreaterThan 大于
toBeGreaterThanOrEqual 至少（大于等于）
toBeLessThan 小于
toBeLessThanOrEqual 最多（小于等于）
toBeCloseTo 用来匹配浮点数（带小数点的相等）
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