Jest - resetting value in module and reloading import - jestjs

Question

I'm writing a test in jest for a module which uses a constant from a different module.
I want to set a different value for it for every test case, but I don't seem to be able to do so.
The test file:
import { Request, Response } from 'express';
const activityConsumer = require('../../src/utils/activity.consumer');
const mockRequest = {
params: {
activityArn: 'activityArn'
}
} as Request;
const mockedJsonFunction = jest.fn();
const mockResponse: any = {
json: jest.fn(),
status: jest.fn().mockReturnValue({ json: mockedJsonFunction }),
} as Response;
let stopConsumerMock;
describe('consumer handler', () => {
beforeAll(() => {
stopConsumerMock = activityConsumer.stopConsumer = jest.fn().mockReturnValue(1);
});
beforeEach(() => {
jest.resetModules();
});
afterEach(() => {
stopConsumerMock.mockClear();
mockResponse.json.mockClear();
});
describe('stopConsumingHandler', () => {
it('Should return success true and not call stopConsumer when no consumer exists', () => {
activityConsumer.consumer = undefined;
const { stopConsumingHandler } = require ('../../src/handlers/consumer.handlers');
stopConsumingHandler(mockRequest, mockResponse);
expect(stopConsumerMock.mock.calls.length).toEqual(0);
expect(mockResponse.json.mock.calls.length).toEqual(1);
expect(mockResponse.json).toHaveBeenCalledWith({ success: true });
});
it('Should return success true and call stopConsumer when consumer exists', () => {
activityConsumer.consumer = true;
const { stopConsumingHandler } = require ('../../src/handlers/consumer.handlers');
stopConsumingHandler(mockRequest, mockResponse);
expect(stopConsumerMock.mock.calls.length).toEqual(1);
expect(mockResponse.json.mock.calls.length).toEqual(1);
expect(mockResponse.json).toHaveBeenCalledWith({ success: true });
});
});
});
I want to replace the value of activityConsumer.consumer and then reload the consumer.handlers module but the re-assignment and reload does not seem to have any effect.
Please advise on how can I write this test properly.

Answer 1

Try this way, using jest.mock to modify import value of activityConsumer
import { Request, Response } from 'express';
// const activityConsumer = require('../../src/utils/activity.consumer');
const mockRequest = {
params: {
activityArn: 'activityArn'
}
} as Request;
const mockedJsonFunction = jest.fn();
const mockResponse: any = {
json: jest.fn(),
status: jest.fn().mockReturnValue({ json: mockedJsonFunction }),
} as Response;
let stopConsumerMock;
describe('consumer handler', () => {
beforeAll(() => {
// stopConsumerMock = activityConsumer.stopConsumer = jest.fn().mockReturnValue(1);
stopConsumerMock = jest.fn().mockReturnValue(1);
});
beforeEach(() => {
jest.resetModules(); // important line
});
afterEach(() => {
stopConsumerMock.mockClear();
mockResponse.json.mockClear();
});
describe('stopConsumingHandler', () => {
it('Should return success true and not call stopConsumer when no consumer exists', () => {
// activityConsumer.consumer = undefined;
// mock by this way
jest.mock('../../src/utils/activity.consumer', () => ({
consumer: undefined,
stopConsumer: stopConsumerMock,
}));
const { stopConsumingHandler } = require('../../src/handlers/consumer.handlers');
stopConsumingHandler(mockRequest, mockResponse);
expect(stopConsumerMock.mock.calls.length).toEqual(0);
expect(mockResponse.json.mock.calls.length).toEqual(1);
expect(mockResponse.json).toHaveBeenCalledWith({ success: true });
});
it('Should return success true and call stopConsumer when consumer exists', () => {
// activityConsumer.consumer = true;
// mock by this way
jest.mock('../../src/utils/activity.consumer', () => ({
consumer: true, // mock value for consumer
stopConsumer: stopConsumerMock,
}));
const { stopConsumingHandler } = require('../../src/handlers/consumer.handlers');
stopConsumingHandler(mockRequest, mockResponse);
expect(stopConsumerMock.mock.calls.length).toEqual(1);
expect(mockResponse.json.mock.calls.length).toEqual(1);
expect(mockResponse.json).toHaveBeenCalledWith({ success: true });
});
});
});