I am trying to learn vitest, in my createUser controller I generate a hashed password using genSalt and hash from bcryptjsin my test file I mocked the two functions using this way

vi.mock("bcryptjs", () => ({
  genSalt: vi.fn(),
  hash: vi.fn(),
}));

it works but i wanted to write a test that makes sure that the password in the user object is a hashed password, so I wanted to restore the original implementation of genSalt and hash, I found a tutorial online that says I should import the acutal module using vi.importActual and mock the two functions implementation with the original imports.

it("User is created with a hashed password", async () => {
    req.body = { name: "foo", email: "[email protected]", password: "1234" };

    const genSaltOriginal = (await vi.importActual<any>("bcryptjs")).genSalt;
    const hashOriginal = (await vi.importActual<any>("bcryptjs")).hash;

    (genSalt as Mock).mockImplementationOnce(genSaltOriginal);
    (hash as Mock).mockImplementationOnce(hashOriginal);

    await createUser(req as Request, res as Response, fakeNext as NextFunction);

This does not work, when I log the salt and hashed password values they return undefined, and for some reason when I comment out (hash as Mock).mockImplementationOnce(hashOriginal) the genSalt works and returns an actual salt when I log it to the console, but enabling this line breaks it, also here is the code for hash generation:

let salt;
  let hashedPassword;

  try {
    salt = await genSalt(10);
    hashedPassword = await hash(password, salt);
  } catch (err) {
    next(new CustomError(undefined, 500, `Password hashing failed\n${err}`));
    return;
  }

I am trying to learn vitest, in my createUser controller I generate a hashed password using genSalt and hash from bcryptjsin my test file I mocked the two functions using this way

vi.mock("bcryptjs", () => ({
  genSalt: vi.fn(),
  hash: vi.fn(),
}));

it works but i wanted to write a test that makes sure that the password in the user object is a hashed password, so I wanted to restore the original implementation of genSalt and hash, I found a tutorial online that says I should import the acutal module using vi.importActual and mock the two functions implementation with the original imports.

it("User is created with a hashed password", async () => {
    req.body = { name: "foo", email: "[email protected]", password: "1234" };

    const genSaltOriginal = (await vi.importActual<any>("bcryptjs")).genSalt;
    const hashOriginal = (await vi.importActual<any>("bcryptjs")).hash;

    (genSalt as Mock).mockImplementationOnce(genSaltOriginal);
    (hash as Mock).mockImplementationOnce(hashOriginal);

    await createUser(req as Request, res as Response, fakeNext as NextFunction);

This does not work, when I log the salt and hashed password values they return undefined, and for some reason when I comment out (hash as Mock).mockImplementationOnce(hashOriginal) the genSalt works and returns an actual salt when I log it to the console, but enabling this line breaks it, also here is the code for hash generation:

let salt;
  let hashedPassword;

  try {
    salt = await genSalt(10);
    hashedPassword = await hash(password, salt);
  } catch (err) {
    next(new CustomError(undefined, 500, `Password hashing failed\n${err}`));
    return;
  }

• javascript
• unit-testing
• hash
• bcrypt
• vitest

1 Answer 1

I managed to fix it, I just invoked the original functions inside the test, then mocked genSalt and hash with the results.

const genSaltOriginal = (await vi.importActual<any>("bcryptjs")).genSalt;
const hashOriginal = (await vi.importActual<any>("bcryptjs")).hash;

const salt = await genSaltOriginal(10);
const hashedPassword = await hashOriginal(password, salt);

(genSalt as Mock).mockResolvedValueOnce(salt);
(hash as Mock).mockResolvedValueOnce(hashedPassword);