unit-testing - Jest mock /监视 Mongoose 链式(查找、排序、限制、跳过)方法

Question

我想要做什么:

监视链接到 find() 上的方法调用在静态模型方法定义中使用

链式方法:sort() , limit() , skip()

示例调用

目标:监视传递给静态模型方法定义中每个方法的参数:

... 静态方法定义

const 结果 = await this.find({}).sort({}).limit().skip();

... 静态方法定义

做了什么find()作为参数接收:完成 findSpy

做了什么sort()作为参数接收:不完整

做了什么limit()作为参数接收:不完整

做了什么skip()作为参数接收:不完整

我尝试过的:

mockingoose库，但仅限于 find()

我已经能够成功模拟 find()方法本身，而不是它之后的链式调用

const findSpy = jest.spyOn(models.ModelName, 'find');

研究模拟链式方法调用但没有成功

Answer 1

我无法在任何地方找到解决方案。这是我最终解决这个问题的方法。 YMMV，如果您知道更好的方法，请告诉我!

给出一些上下文，这是 REST implementation of the Medium.com API 的一部分我正在作为一个副项目工作。

我是如何 mock 他们的

我模拟了每个链接方法，并设计为返回模型模拟对象本身，以便它可以访问链中的下一个方法。

链中的最后一个方法 (skip) 旨在返回结果。

在测试本身中，我使用了 Jest mockImplementation()为每个测试设计其行为的方法

然后可以使用 expect(StoryMock.chainedMethod).toBeCalled[With]() 监视所有这些。

const StoryMock = {
  getLatestStories, // to be tested
  addPagination: jest.fn(), // already tested, can mock
  find: jest.fn(() => StoryMock),
  sort: jest.fn(() => StoryMock),
  limit: jest.fn(() => StoryMock),
  skip: jest.fn(() => []),
};

要测试的静态方法定义

/**
 * Gets the latest published stories
 * - uses limit, currentPage pagination
 * - sorted by descending order of publish date
 * @param {object} paginationQuery pagination query string params
 * @param {number} paginationQuery.limit [10] pagination limit
 * @param {number} paginationQuery.currentPage [0] pagination current page
 * @returns {object} { stories, pagination } paginated output using Story.addPagination
 */
async function getLatestStories(paginationQuery) {
  const { limit = 10, currentPage = 0 } = paginationQuery;

  // limit to max of 20 results per page
  const limitBy = Math.min(limit, 20);
  const skipBy = limitBy * currentPage;

  const latestStories = await this
    .find({ published: true, parent: null }) // only published stories
    .sort({ publishedAt: -1 }) // publish date descending
    .limit(limitBy)
    .skip(skipBy);

  const stories = await Promise.all(latestStories.map(story => story.toResponseShape()));

  return this.addPagination({ output: { stories }, limit: limitBy, currentPage });
}

完整的 Jest 测试以查看模拟的实现

const { mocks } = require('../../../../test-utils');
const { getLatestStories } = require('../story-static-queries');

const StoryMock = {
  getLatestStories, // to be tested
  addPagination: jest.fn(), // already tested, can mock
  find: jest.fn(() => StoryMock),
  sort: jest.fn(() => StoryMock),
  limit: jest.fn(() => StoryMock),
  skip: jest.fn(() => []),
};

const storyInstanceMock = (options) => Object.assign(
  mocks.storyMock({ ...options }),
  { toResponseShape() { return this; } }, // already tested, can mock
); 

describe('Story static query methods', () => {
  describe('getLatestStories(): gets the latest published stories', () => {
    const stories = Array(20).fill().map(() => storyInstanceMock({}));

    describe('no query pagination params: uses default values for limit and currentPage', () => {
      const defaultLimit = 10;
      const defaultCurrentPage = 0;
      const expectedStories = stories.slice(0, defaultLimit);

      // define the return value at end of query chain
      StoryMock.skip.mockImplementation(() => expectedStories);
      // spy on the Story instance toResponseShape() to ensure it is called
      const storyToResponseShapeSpy = jest.spyOn(stories[0], 'toResponseShape');

      beforeAll(() => StoryMock.getLatestStories({}));
      afterAll(() => jest.clearAllMocks());

      test('calls find() for only published stories: { published: true, parent: null }', () => {
        expect(StoryMock.find).toHaveBeenCalledWith({ published: true, parent: null });
      });

      test('calls sort() to sort in descending publishedAt order: { publishedAt: -1 }', () => {
        expect(StoryMock.sort).toHaveBeenCalledWith({ publishedAt: -1 });
      });

      test(`calls limit() using default limit: ${defaultLimit}`, () => {
        expect(StoryMock.limit).toHaveBeenCalledWith(defaultLimit);
      });

      test(`calls skip() using <default limit * default currentPage>: ${defaultLimit * defaultCurrentPage}`, () => {
        expect(StoryMock.skip).toHaveBeenCalledWith(defaultLimit * defaultCurrentPage);
      });

      test('calls toResponseShape() on each Story instance found', () => {
        expect(storyToResponseShapeSpy).toHaveBeenCalled();
      });

      test(`calls static addPagination() method with the first ${defaultLimit} stories result: { output: { stories }, limit: ${defaultLimit}, currentPage: ${defaultCurrentPage} }`, () => {
        expect(StoryMock.addPagination).toHaveBeenCalledWith({
          output: { stories: expectedStories },
          limit: defaultLimit,
          currentPage: defaultCurrentPage,
        });
      });
    });

    describe('with query pagination params', () => {
      afterEach(() => jest.clearAllMocks());

      test('executes the previously tested behavior using query param values: { limit: 5, currentPage: 2 }', async () => {
        const limit = 5;
        const currentPage = 2;
        const storyToResponseShapeSpy = jest.spyOn(stories[0], 'toResponseShape');
        const expectedStories = stories.slice(0, limit);

        StoryMock.skip.mockImplementation(() => expectedStories);

        await StoryMock.getLatestStories({ limit, currentPage });
        expect(StoryMock.find).toHaveBeenCalledWith({ published: true, parent: null });
        expect(StoryMock.sort).toHaveBeenCalledWith({ publishedAt: -1 });
        expect(StoryMock.limit).toHaveBeenCalledWith(limit);
        expect(StoryMock.skip).toHaveBeenCalledWith(limit * currentPage);
        expect(storyToResponseShapeSpy).toHaveBeenCalled();
        expect(StoryMock.addPagination).toHaveBeenCalledWith({
          limit,
          currentPage,
          output: { stories: expectedStories },
        });
      });

      test('limit value of 500 passed: enforces maximum value of 20 instead', async () => {
        const limit = 500;
        const maxLimit = 20;
        const currentPage = 2;
        StoryMock.skip.mockImplementation(() => stories.slice(0, maxLimit));

        await StoryMock.getLatestStories({ limit, currentPage });
        expect(StoryMock.limit).toHaveBeenCalledWith(maxLimit);
        expect(StoryMock.addPagination).toHaveBeenCalledWith({
          limit: maxLimit,
          currentPage,
          output: { stories: stories.slice(0, maxLimit) },
        });
      });
    });
  });
});