Dealing with throwing Exceptions in jest: A guide for developers

Question

Dealing with throwing Exceptions in jest: A guide for developers

I have developed a method that throws an exception when the provided password does not match a regex pattern. I attempted to handle this in Jest.

  it('Should prevent insertion of a new user if the password doesn't match the regex', async () => {
    jest.spyOn(usersModel, 'create').mockImplementationOnce(() =>
      Promise.resolve({
        name: 'some name',
        email: 'some <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="ff9a929e9693bf9a929e9693d19c9092">[email protected]</a>',
        pass: 'some pass',
      } as IUser)
    )

    const newUser = await usersService.create({
      name: 'some name',
      email: 'some <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="abcec6cac2c7ebcec6cac2c785c8c4c6">[email protected]</a>',
      pass: 'some pass',
    })
    expect(newUser).toThrow()
  })

I also tried using toThrow('error message') and

toThrow(new BadRequestException())

, but neither of them worked.

Here is the error message from Jest:

 UsersService › Should not insert a new user cause password do not match regex

    Password does not match regex

      49 |     const emailRegex = /[^@ \t\r\n]+@[^@ \t\r\n]+\.[^@ \t\r\n]+/
      50 |
    > 51 |     if (!pass.match(passRegex)) throw new BadRequestException('Password does not match regex')
         |                                       ^
      52 |     if (!email.match(emailRegex)) throw new BadRequestException('Email does not match regex')
      53 |
      54 |     const saltRounds = 10

      at UsersService.create (users/users.service.ts:51:39)
      at Object.<anonymous> (users/users.service.spec.ts:135:21)

javascript typescript exception jestjs nestjs

Answer 1

Answer №1

To validate the password against a regex pattern when inserting a new user, you can utilize the .resolves matcher within your expect statement as shown below:

it('Should not insert a new user cause password do not match regex', async () => {
  jest.spyOn(usersModel, 'create').mockImplementationOnce(() =>
    Promise.resolve({
      name: 'some name',
      email: 'some <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="94f1f9f5fdf8d4f1f9f5fdf8baf7fbf9">[email protected]</a>',
      pass: 'some pass',
    } as IUser),
  );

  // Remove `await` keyword, because you will pass a promise in the expect function
  const newUser = usersService.create({
    name: 'some name',
    email: 'some <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="07626a666e6b47626a666e6b2964686a">[email protected]</a>',
    pass: 'some pass',
  });

  // Add `await` keyword and `rejects` matcher with the `toThrow`
  await expect(newUser).rejects.toThrow('Password does not match regex');
});

If desired, an alternative approach using a try/catch statement is presented below (although it's recommended to stick with the previous method):

it('Should not insert a new user cause password do not match regex', async () => {
  expect.assertions(1)

  jest.spyOn(usersModel, 'create').mockImplementationOnce(() =>
    Promise.resolve({
      name: 'some name',
      email: 'some <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="dabfb7bbb3b69abfb7bbb3b6f4b9b5b7">[email protected]</a>',
      pass: 'some pass',
    } as IUser),
  );

  // Incorporate a `try/catch` statement
  try {
    const newUser = await usersService.create({
      name: 'some name',
      email: 'some <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="2e4b434f47426e4b434f4742004d4143">[email protected]</a>',
      pass: 'some pass',
    });
  } catch (e) {
    expect(e.toString()).toMatch('Password does not match regex');
  }
});

Answer 2

To validate the password against a regex pattern when inserting a new user, you can utilize the .resolves matcher within your expect statement as shown below:

it('Should not insert a new user cause password do not match regex', async () => {
  jest.spyOn(usersModel, 'create').mockImplementationOnce(() =>
    Promise.resolve({
      name: 'some name',
      email: 'some <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="94f1f9f5fdf8d4f1f9f5fdf8baf7fbf9">[email protected]</a>',
      pass: 'some pass',
    } as IUser),
  );

  // Remove `await` keyword, because you will pass a promise in the expect function
  const newUser = usersService.create({
    name: 'some name',
    email: 'some <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="07626a666e6b47626a666e6b2964686a">[email protected]</a>',
    pass: 'some pass',
  });

  // Add `await` keyword and `rejects` matcher with the `toThrow`
  await expect(newUser).rejects.toThrow('Password does not match regex');
});

If desired, an alternative approach using a try/catch statement is presented below (although it's recommended to stick with the previous method):

it('Should not insert a new user cause password do not match regex', async () => {
  expect.assertions(1)

  jest.spyOn(usersModel, 'create').mockImplementationOnce(() =>
    Promise.resolve({
      name: 'some name',
      email: 'some <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="dabfb7bbb3b69abfb7bbb3b6f4b9b5b7">[email protected]</a>',
      pass: 'some pass',
    } as IUser),
  );

  // Incorporate a `try/catch` statement
  try {
    const newUser = await usersService.create({
      name: 'some name',
      email: 'some <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="2e4b434f47426e4b434f4742004d4143">[email protected]</a>',
      pass: 'some pass',
    });
  } catch (e) {
    expect(e.toString()).toMatch('Password does not match regex');
  }
});

Dealing with throwing Exceptions in jest: A guide for developers

Answer №1

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