jest-save-mongoose.js

//Test file

const TodoController = require("../../controllers/todo.controller");
const TodoModel = require("../../model/todo.model");
const httpMocks = require("node-mocks-http");
const newTodo = require("../mock-data/new-todo.json");

// jest.mock("../../model/todo.model"); cant use this with the prototype.save

const saveMock = jest.fn();
TodoModel.prototype.save = saveMock;

let req, res, next;
beforeEach(() => {
  req = httpMocks.createRequest();
  res = httpMocks.createResponse();
  next = jest.fn();
});

describe("TodoController.SaveTodo", () => {
  beforeEach(() => {
    req.body = newTodo;
  });

  it("should have a saveTodo function", () => {
    expect(typeof TodoController.saveTodo).toBe("function");
  });

  it("should call TodoModel.save", () => {
    TodoController.saveTodo(req, res, next);
    expect(saveMock).toHaveBeenCalled();
  });
});

//Controller file
const TodoModel = require("../model/todo.model");

exports.saveTodo = async (req, res, next) => {
  try {
    console.log(TodoModel);
    const createdModel = await TodoModel.create(req.body);
    console.log(createdModel);
    createdModel.save();
  } catch (err) {
    next(err);
  }
};

He @Hyllesen this code is not able to mock the save method. Your 3rd test case is failing.
I am trying to mock save from a long time.
Please can you provide some solution. It will be very helpful for me.

How to mock save() ???

This does not seem to work ! The save function gives an error while unit testing !

--------- This is the error message --------------

TodoController.SaveTodo › should call TodoModel.save

expect(jest.fn()).toHaveBeenCalled()

Expected number of calls: >= 1
Received number of calls:    0

  35 |   it("should call TodoModel.save", () => {
  36 |     todoController.saveTodo(req, res, next);
> 37 |     expect(saveMock).toHaveBeenCalled();
     |                      ^
  38 |   });
  39 | });
  40 |

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