Jest reset mock of a node module - jestjs

Question

I'm working on the Google Cloud Functions tests.
The files are these:
index.ts which only exports the functions which are also imported there.
if (!process.env.FUNCTION_NAME || process.env.FUNCTION_NAME === 'contactSupportByMail') {
exports.contactSupportByMail = require('./contactSupportByMail');
}
contactSupportByMail.ts the function to test.
And the test:
describe('Cloud Functions', (): void => {
let myFunctions;
let adminInitStub;
beforeAll((): void => {
// [START stubAdminInit]
// If index.js calls admin.initializeApp at the top of the file,
// we need to stub it out before requiring index.js. This is because the
// functions will be executed as a part of the require process.
// Here we stub admin.initializeApp to be a dummy function that doesn't do anything.
adminInitStub = sinon.stub(admin, 'initializeApp');
testEnv.mockConfig({
sendgrid: {
key: 'apiKey',
},
brand: {
support_email: 'supportEmail',
},
});
// [END stubAdminInit]
});
afterAll((): void => {
// Restore admin.initializeApp() to its original method.
adminInitStub.restore();
// Do other cleanup tasks.
process.env.FUNCTION_NAME = '';
myFunctions = undefined;
testEnv.cleanup();
});
describe('contactSupportByMail', (): void => {
// Mocking node_modules library before the require
jest.mock('#sendgrid/mail', (): { [key: string]: any } => ({
setApiKey: (): void => { },
send: (): Promise<any> => Promise.resolve('ok'),
}));
// Setting up cloud function name
process.env.FUNCTION_NAME = 'contactSupportByMail';
// Importing the index file
myFunctions = require('../src/index');
const wrapped = testEnv.wrap(myFunctions.contactSupportByMail);
it('it should export contactSupportByMail', (): void => {
const cFunction = require('../src/contactSupportByMail');
assert.isObject(myFunctions);
assert.include(myFunctions, { contactSupportByMail: cFunction });
});
it('should fully work', async (): Promise<void> => {
const onCallObjects: [any, ContextOptions] = [
{ mailBody: 'mailBody', to: 'toEmail' },
{ auth: { token: { email: 'userEmail' } } },
];
return assert.deepEqual(await wrapped(...onCallObjects), { ok: true });
});
it('not auth', async (): Promise<void> => {
await expect(wrapped(undefined)).rejects.toThrow('The function must be called while authenticated.');
});
it('sendgrid error', async (): Promise<void> => {
// Mocking node_modules library before the require
jest.mock('#sendgrid/mail', (): { [key: string]: any } => ({
setApiKey: (): void => { },
send: (): Promise<any> => Promise.reject('errorsengrid'),
}));
// Importing the index file
const a = require('../src/index');
const wrapped_2 = testEnv.wrap(a.contactSupportByMail);
const onCallObjects: [any, ContextOptions] = [
{ mailBody: 'mailBody', to: 'toEmail' },
{ auth: { token: { email: 'userEmail' } } },
];
await expect(wrapped_2(...onCallObjects)).rejects.toThrow('errorsengrid');
});
});
});
The problem is provoking the sendgrid error. I don't know how to reset the mock of sendgrid's library which is required inside contactSupportByMail. After mocking it for the first time, it always returns the send function as resolved.

Answer 1

Just a note - if using babel-jest, mock calls are hoisted to the top of the transpiled js... doMock allow you to mock in the before functions of a test.
This is one way to mock a module for some tests within a file - and restore it for the others:
describe("some tests", () => {
let subject;
describe("with mocks", () => {
beforeAll(() => {
jest.isolateModules(() => {
jest.doMock("some-lib", () => ({ someFn: jest.fn() }));
subject = require('./module-that-imports-some-lib');
});
});
// ... tests when some-lib is mocked
});
describe("without mocks - restoring mocked modules", () => {
beforeAll(() => {
jest.isolateModules(() => {
jest.unmock("some-lib");
subject = require('./module-that-imports-some-lib');
});
});
// ... tests when some-lib is NOT mocked
});
});

Answer 2

I finally got the solution:
afterEach((): void => {
jest.resetModules();
});