Jest mocking / spying on Mongoose chained (find, sort, limit, skip) methods - unit-testing

Question

What I am looking to do:
spy on the method calls chained onto find() used in a static Model method definition
chained methods: sort(), limit(), skip()
Sample call
goal: to spy on the arguments passed to each of the methods in a static Model method definition:
... static method def
const results = await this.find({}).sort({}).limit().skip();
... static method def
what did find() receive as args: completed with findSpy
what did sort() receive as args: incomplete
what did limit() receive as args: incomplete
what did skip() receive as args: incomplete
What I have tried:
the mockingoose library but it is limited to just find()
I have been able to successfully mock the find() method itself but not the chained calls that come after it
const findSpy = jest.spyOn(models.ModelName, 'find');
researching for mocking chained method calls without success

Answer 1

I was not able to find a solution anywhere. Here is how I ended up solving this. YMMV and if you know of a better way please let me know!
To give some context this is part of a REST implementation of the Medium.com API I am working on as a side project.
How I mocked them
I had each chained method mocked and designed to return the Model mock object itself so that it could access the next method in the chain.
The last method in the chain (skip) was designed to return the result.
In the tests themselves I used the Jest mockImplementation() method to design its behavior for each test
All of these could then be spied on using expect(StoryMock.chainedMethod).toBeCalled[With]()
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(() => []),
};
Static method definition to be tested
/**
* 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 });
}
Full Jest tests to see implementation of the mock
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) },
});
});
});
});
});

Answer 2

jest.spyOn(Post, "find").mockImplementationOnce(() => ({
sort: () => ({
limit: () => [{
id: '613712f7b7025984b080cea9',
text: 'Sample text'
}],
}),
}));

Answer 3

Here is how I did this with sinonjs for the call:
await MyMongooseSchema.find(q).skip(n).limit(m)
It might give you clues to do this with Jest:
sinon.stub(MyMongooseSchema, 'find').returns(
{
skip: (n) => {
return {
limit: (m) => {
return new Promise((
resolve, reject) => {
resolve(searchResults);
});
}
}
}
});
sinon.stub(MyMongooseSchema, 'count').resolves(searchResults.length);

Answer 4

This worked for me:
jest.mock("../../models", () => ({
Action: {
find: jest.fn(),
},
}));
Action.find.mockReturnValueOnce({
readConcern: jest.fn().mockResolvedValueOnce([
{ name: "Action Name" },
]),
});

Answer 5

All the above didn't work in my case, after some trial and error this worked for me:
const findSpy = jest.spyOn(tdataModel.find().sort({ _id: 1 }).skip(0).populate('fields'), 'limit')
NOTE: you need to mock the query, in my case I use NestJs:
I did the following:
find: jest.fn().mockImplementation(() => ({
sort: jest.fn().mockImplementation((...args) => ({
skip: jest.fn().mockImplementation((...arg) => ({
populate: jest.fn().mockImplementation((...arg) => ({
limit: jest.fn().mockImplementation((...arg) => telemetryDataStub),
})),
})),
})),
})),
findOne: jest.fn(),
updateOne: jest.fn(),
deleteOne: jest.fn(),
create: jest.fn(),
count: jest.fn().mockImplementation(() => AllTelemetryDataStub.length),

Answer 6

for me it worked like this:
AnyModel.find = jest.fn().mockImplementationOnce(() => ({
limit: jest.fn().mockImplementationOnce(() => ({
sort: jest.fn().mockResolvedValue(mock)
}))
}))