Mocha.js:异步函数打破嵌套结构

Question

当使用mocha测试异步函数的结果时，await之后的测试会从嵌套结构中弹出，比如下面的前两个测试：

✓ email
✓ phone
current unit
    fetch data
    ✓ is 5==5

3 passing (10ms)

我们怎样才能让测试出现在合适的位置呢？

代码：

const chai = require('chai');
chai.should();

describe ("current unit", async () => {    
    describe ("fetch data", async () => {    
        it ("is 5==5", () => { chai.expect(5).to.equal(5); });

        const UserData = await getUserData("UserName");

        it ("email", () => { UserData.email.should.equal("example@g.com"); });
        it ("phone", () => { UserData.phone.should.equal("+1 (800) 123 4567"); });
    });
});

function getUserData(param) { return new Promise(resolve => setTimeout(() => resolve({ email:"example@g.com",phone:"+1 (800) 123 4567" }), 1/*ms*/));}

Answer 1

这是使用before的测试文件

const chai = require('chai');
chai.should();

describe ("current unit", async () => {    
    describe ("fetch data", async () => {    
        let UserData
        before(async () => {
            UserData = await getUserData("UserName");
        })
        it ("is 5==5", () => { chai.expect(5).to.equal(5); });
        it ("email", () => { UserData.email.should.equal("example@g.com"); });
        it ("phone", () => { UserData.phone.should.equal("+1 (800) 123 4567"); });
    });
});

function getUserData(param) { return new Promise(resolve => setTimeout(() => resolve({ email:"example@g.com",phone:"+1 (800) 123 4567" }), 1/*ms*/));}

以下是上述测试的输出

  current unit
    fetch data
      ✓ is 5==5
      ✓ email
      ✓ phone

通过使用"fetch data“测试套件中的before表达式，可以使测试显示在适当的位置

Answer 2

如果您将代码从async/await语法“转换”为Promise语法，那么解释起来会更加清晰：

describe("current unit", () => {
  describe("fetch data", () => {
    it("is 5==5", () => { chai.expect(5).to.equal(5); });

    getUserData("UserName")
      .then(UserData => {
        it("email", () => { UserData.email.should.equal("example@g.com"); });
        it("phone", () => { UserData.phone.should.equal("+1 (800) 123 4567"); });
      });
  });
});

如你所见，"fetch data“只包括is 5==5，而email，phone规范在另一个作用域中(在本例中，作用域是free describe)，那么这些规范将出现在顶部。

getUserData只是“等待”1ms，然后您可以看到email，phone规范，如果您将该值增加到100ms (或更高)，您将不会看到这些规范，因为getUserData().then是一个同步块。

千万不要在describe的body中直接调用异步动作，让我们使用beforeEach，或者写在it的body中。

使用beforeEach

describe("current unit", () => { // remove async keyword, it does not make sense
  let UserData; // define variable
  beforeEach(async () => { // async
    UserData = await getUserData("UserName"); // init
  });

  describe("fetch data", () => { // remove async keyword
    it("is 5==5", () => { chai.expect(5).to.equal(5); });
    it("email", () => { UserData.email.should.equal("example@g.com"); });
    it("phone", () => { UserData.phone.should.equal("+1 (800) 123 4567"); });
  });
});

  current unit
    fetch data
      ✓ is 5==5
      ✓ email
      ✓ phone
  3 passing (357ms)

在it块中写入：

describe("current unit", () => { // remove async keyword, it does not make sense
  describe("fetch data", () => { // remove async keyword
    it("is 5==5", () => { chai.expect(5).to.equal(5); });
    it("should return correct email and phone", async () => { // compile into 1 spec
      const UserData = await getUserData("UserName");
      UserData.email.should.equal("example@g.com");
      UserData.phone.should.equal("+1 (800) 123 4567");
    });
  });
});

  current unit
    fetch data
      ✓ is 5==5
      ✓ should return correct email and phone (108ms)
  2 passing (149ms)

Answer 3

您需要在测试的异步部分之后调用done()函数。下面是一个例子：

it ("email", (done) => {
  UserData.email.should.equal("example@g.com");
  done();
});