Unexpected error (without message) of "toHaveBeenLastCalledWith"

[chris-visser]

I've stumbled upon an issue where Jest is not clear to me and throw's an invalid error without a message:

Error: expect(jest.fn()).toHaveBeenLastCalledWith(expected)

Expected mock function to have been last called with:


      368 |     it('Should call the storage assignRole method with the right parameters', () => {
      369 |       Privileges.assignRole('chris', 'admin');
    > 370 |       expect(mockStorage.assignRole).toHaveBeenLastCalledWith('chris', 'admin');
      371 |     });
      372 |   });
      373 | 
      
      at Object.it (lib/privileges.test.js:370:38)

After some research I found out that the error is thrown, because i'm pushing a 3th parameter with an undefined value into my jest mock function like shown below:

  // Calling this method with assignRole('chris', 'admin')
  assignRole(userId, role, group) {
    // Below 'assignRole' method call is mocked. group === undefined
    return this.storage.assignRole(userId, role, group);
  }

On the other hand, testing it with explicitly checking for undefined will result in a valid test:

    it('Should call the storage assignRole method with the right parameters', () => {
      Privileges.assignRole('chris', 'admin');
      expect(mockStorage.assignRole).toHaveBeenLastCalledWith('chris', 'admin', undefined);
    });

I would expect Jest not to throw any error when I'm not checking the 3th parameter. If it does need to throw any error, because I am passing the group parameter (explicitly checking all parameters) then I would expect Jest to throw me an error along the lines of "Expected mock function to have been last called with 2 parameters. Instead it was called with 3."

I'm using the latest Jest version "22.1.4".

Thank you!

[SimenB]

Duplicate of #5197.

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