Jest测试初学（二）--Jest 中的匹配器

一 修改配置

让Jest监听所有测试（test.js）文件的变化，如果有变化就自动跑测试用例

  "scripts": {
    "test": "jest --watchAll",
    "coverage": "jest --coverage"
  },

二 部分匹配器

运行测试用例 jest自带test和expect方法

比较结果的匹配器

• toBe

test('测试加法 3+7', () => {
    //toBe为匹配器  matchers
    // expect(10).toBe(10);
    //toBe相当于js中的 object.is  ===
    const a = { one : 1 };
    expect(a).toBe({ one : 1 });
});

• toEqual

test('测试加法 3+7', () => {
    //toEqual为匹配器  
    const a = { one : 1 };
    expect(a).toEqual({ one : 1 });
});

• toBeNull

test('测试加法 3+7', () => {
    // const a = null;
    const a = undefined;
    expect(a).toBeNull();
});

真假有关的匹配器

• toBeUndefined

test('toBeUndefined', () => {
    const a = undefined;
    expect(a).toBeUndefined();
});

• toBeDefined

test('toBeDefined', () => {
    const a = 1;
    expect(a).toBeDefined();
});

• toBeTruthy

test('toBeTruthy', () => {
    const a = 1;
    // const a = null;
    expect(a).toBeTruthy();
});

• toBeFalsy

test('toBeFalsy', () => {
    // const a = 1;
    const a = 0;
    expect(a).toBeFalsy();
});

test('not', () => {
    const a = 1;
    // const a = 0;
    expect(a).not.toBeFalsy();
});

数字相关的匹配器

• toBeGreaterThan

test('toBeGreaterThan', () => {
    const count = 10;
    expect(count).toBeGreaterThan(3);
});

• toBeLessThan

test('toBeLessThan', () => {
    const count = 10;
    expect(count).toBeLessThan(13);
});

• toBeGreaterThanOrEqual

test('toBeGreaterThanOrEqual', () => {
    const count = 10;
    expect(count).toBeGreaterThanOrEqual(8);
});

• toBeLessThanOrEqual

test('toBeLessThanOrEqual', () => {
    const count = 10;
    expect(count).toBeLessThanOrEqual(14);
});

• toBeCloseTo

test('toBeCloseTo', () => {
    const firstNumber = 0.1;
    const secondNumber = 0.2;
    // expect(firstNumber + secondNumber).toEqual(0.3);
    expect(firstNumber + secondNumber).toBeCloseTo(0.3);
});

String匹配器

• toMatch

test('toMatch', () => {
    const str = 'http://www.dell-lee.com';
    expect(str).toMatch(/dell-lee/);
});

Array Set匹配器

• toContain

test('toContain', () => {
    const arr = ['dell','lee','imooc'];
    const data = new Set(arr);
    expect(data).toContain('dell');
});

异常

• toThrow

const throwNewErrorFunc = () => {
    throw new Error('this  is a new error');
}
test('toThrow', () => {
    // expect(throwNewErrorFunc).not.toThrow('this is a new error');
    expect(throwNewErrorFunc).not.toThrow(/this is a new error/);
});
//两处的error信息要一致，否则报错