如何使用 JEST 在方法中模拟方法？答案

【问题标题】：How to mock a method inside a method using JEST?如何使用 JEST 在方法中模拟方法？
【发布时间】：2020-03-31 02:49:54
【问题描述】：

我正在尝试对一个名为search 的方法进行单元测试，该方法具有buildSearchParameter、isUnknownFields、readAll 等三种方法。我需要嘲笑他们，但我不知道该怎么做。谁能帮我解决这个问题？

【问题讨论】：

标签： javascript node.js typescript unit-testing jestjs

【解决方案1】：

为了简化问题，我删除了它的静态类型。您可以使用jest.spyOn 为这三种方法制作存根。这是单元测试解决方案：

index.ts:

import ModelUtility from './ModelUtility';

enum EndpointType {
  SEARCH = 'SEARCH',
}

export class SomeClass {
  schemaConstants;
  errorConstants = {
    invalidQueryParameters: 'invalid',
  };

  search = async (query, endpointConstants) => {
    const searchParam = ModelUtility.buildSearchParameter(query, endpointConstants, this.schemaConstants);
    // check for unknown fields
    const isUnknownFields = ModelUtility.isUnknownFields(EndpointType.SEARCH, searchParam, this.schemaConstants);
    if (isUnknownFields) {
      return this.errorConstants.invalidQueryParameters;
    }
    return this.readAll(query, searchParam, endpointConstants);
  };

  readAll(...args) {
    return 'real data';
  }
}

ModelUtility.ts:

export default {
  buildSearchParameter(...args) {
    return 'real search parameter';
  },
  isUnknownFields(...args) {
    return true;
  },
};

index.spec.ts:

import { SomeClass } from './';
import ModelUtility from './ModelUtility';

describe('SomeClass', () => {
  afterEach(() => {
    jest.restoreAllMocks();
  });
  it('should return invalid query parameters', async () => {
    const buildSearchParameterSpy = jest
      .spyOn(ModelUtility, 'buildSearchParameter')
      .mockReturnValueOnce('mocked search parameter');
    const isUnknownFieldsSpy = jest.spyOn(ModelUtility, 'isUnknownFields').mockReturnValueOnce(true);

    const instance = new SomeClass();
    const actual = await instance.search('mocked query', 'endpointConstants');
    expect(actual).toBe('invalid');
    expect(buildSearchParameterSpy).toBeCalledWith('mocked query', 'endpointConstants', undefined);
    expect(isUnknownFieldsSpy).toBeCalledWith('SEARCH', 'mocked search parameter', undefined);
  });

  it('should return correctly', async () => {
    const buildSearchParameterSpy = jest
      .spyOn(ModelUtility, 'buildSearchParameter')
      .mockReturnValueOnce('mocked search parameter');
    const isUnknownFieldsSpy = jest.spyOn(ModelUtility, 'isUnknownFields').mockReturnValueOnce(false);

    const instance = new SomeClass();
    jest.spyOn(instance, 'readAll').mockReturnValueOnce('mocked data');
    const actual = await instance.search('mocked query', 'endpointConstants');
    expect(actual).toBe('mocked data');
    expect(buildSearchParameterSpy).toBeCalledWith('mocked query', 'endpointConstants', undefined);
    expect(isUnknownFieldsSpy).toBeCalledWith('SEARCH', 'mocked search parameter', undefined);
  });
});

带有覆盖率报告的单元测试结果：

 PASS  src/stackoverflow/59207566/index.spec.ts
  SomeClass
    ✓ should return invalid query parameters (7ms)
    ✓ should return correctly (1ms)

-----------------|----------|----------|----------|----------|-------------------|
File             |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
-----------------|----------|----------|----------|----------|-------------------|
All files        |    72.73 |      100 |    57.14 |    73.68 |                   |
 ModelUtility.ts |       20 |      100 |        0 |       20 |           2,3,5,6 |
 index.ts        |    88.24 |      100 |       80 |    92.86 |                24 |
-----------------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       2 passed, 2 total
Snapshots:   0 total
Time:        4.891s, estimated 11s

【讨论】：