Jest - Externalise 扩展期望匹配器答案

【问题标题】：Jest - Externalise extended expect matchersJest - Externalise 扩展期望匹配器
【发布时间】：2021-06-12 10:50:13
【问题描述】：

我有。 node.js-TypeScript applciation 和 Jest 用于测试。使用这个参考https://jestjs.io/docs/expect#expectextendmatchers 我的测试类中有一些扩展的期望匹配器。就像下面的例子一样。我在几个不同的测试类中有很多常见的扩展。有没有办法将这些扩展匹配器外部化/分组并通过导入它们在测试类中使用？

例子：

expect.extend({
  async toBeDivisibleByExternalValue(received) {
    const externalValue = await getExternalValueFromRemoteSource();
    const pass = received % externalValue == 0;
    if (pass) {
      return {
        message: () =>
          `expected ${received} not to be divisible by ${externalValue}`,
        pass: true,
      };
    } else {
      return {
        message: () =>
          `expected ${received} to be divisible by ${externalValue}`,
        pass: false,
      };
    }
  },
});

test('is divisible by external value', async () => {
  await expect(100).toBeDivisibleByExternalValue();
  await expect(101).not.toBeDivisibleByExternalValue();
});

我的笑话.d.ts：

export {};
declare global {
  namespace jest {
    interface Matchers<R> {
      hasTestData(): R;
    }
}

【问题讨论】：

标签： node.js typescript testing jestjs ts-jest

【解决方案1】：

对于常见的扩展期望，我使用以下逻辑；

ExtendedExpects.ts：

declare global {
    namespace jest {
        interface Matchers<R> {
            toBeDivisibleByExternalValue(): R;
        }
    }
}
export function toBeDivisibleByExternalValue(received:any): jest.CustomMatcherResult {
    const externalValue = await getExternalValueFromRemoteSource();
    const pass = received % externalValue == 0;
    if (pass) {
      return {
        message: () =>
          `expected ${received} not to be divisible by ${externalValue}`,
        pass: true,
      };
    } else {
      return {
        message: () =>
          `expected ${received} to be divisible by ${externalValue}`,
        pass: false,
      };
    }
}

你定义了通用方法，现在如何使用它；

你的测试类看起来像，

import { toBeDivisibleByExternalValue } from "../ExtendedExpects";

expect.extend({
   toBeDivisibleByExternalValue
});

test('is divisible by external value', async () => {
  await expect(100).toBeDivisibleByExternalValue();
  await expect(101).not.toBeDivisibleByExternalValue();
});

你不再需要 jest.d.ts。

【讨论】：