开玩笑:测试块之间共享异步代码 [英] Jest: shared async code between test blocks

问题描述

我有一些这样的测试代码:

I have some test code like this:

test('Test', async () => {
  const someData = await setup()
  const actual = myFunc(someData.x)
  expect(actual.a).toEqual(someData.y)
  expect(actual.b).toEqual(someData.y)
  ... many more like this
}

我想将代码分成多个test块(因为我什至无法在每个expect语句中添加描述消息).

I would like to break apart the code into multiple test blocks (because I can't even add a description message to each expect statement).

如果Jest支持异步describe，我可以这样做:

If Jest supported async describe, I could do this:

describe('Some group of tests', async () => {
const someData = await setup()

test('Test1', async () => {
  const actual = myFunc(someData.x)
  expect(actual.a).toEqual(someData.y)
}

test('Test2', async () => {
  const actual = myFunc(someData.x)
  expect(actual.b).toEqual(someData.y)
}
})

我当然可以为每个测试重复设置调用，但这会大大降低测试速度(我在此处填充MongoDB).

I could duplicate the setup call for each test of course, but that would slow down the test considerable (I'm populating MongoDB there).

那么，有什么方法可以改善Jest的测试结构吗?

So, any way I can improve the structure of my test with Jest?

推荐答案

describe回调函数不应该异步是正确的.它会同步定义套件的测试，其范围内的所有异步操作都将被丢弃.

It's correct that describe callback function isn't supposed to be asynchronous. It synchronously defines tests for a suite, any asynchronous operations in its scope will be discarded.

以前，Jasmine和Jest允许使用常规函数和this访问常见的测试上下文. Jest不推荐使用此功能；公用变量需要用户定义.

Previously Jasmine and Jest allowed to access common test context with regular functions and this. This feature was deprecated in Jest; common variables need to be user-defined.

共享的代码可以移到内部使用beforeAll，beforeEach等的帮助器函数中:

Shared code can be moved into helper function that internally uses beforeAll, beforeEach, etc:

const setupWithTestContext = (testContext = {}) => {
  beforeAll(async () => {
    const setupData = await setup();
    Object.assign(testContext, setupData);
  });
  return testContext; // sets up a new one or returns an existing
});

const anotherSetupWithTestContext = (testContext = {}) => {
  beforeEach(() => {
    testContext.foo = 0;
  });
  return testContext;
});

...

describe('Some group of tests', async () => {
    const sharedTestData = setupTestContext();
    // or
    // const sharedTestData = {}; setupTestContext(sharedTestData);

    anotherSetupWithTestContext(sharedTestData);

    test('Test1', async () => {
      // context is filled with data at this point
      const actual = myFunc(sharedTestData.x)
      ...
    }
    ...
})

这篇关于开玩笑:测试块之间共享异步代码的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！