Testing class method that calls an instance variable - AttributeError

Question

How can I mock a class to test its methods in isolation when they use instance variables? This is an example of the code I am trying to test.

class Employee:
    def __init__(self, id):
        self.id = id
        self.email = self.set_email()

    def set_email():
        df = get_all_info()
        return df[df[id] == self.id].email[0]

def get_all_info():
    # ...

My thought is to Mock the Employee class then call the set_email method to test it. The testing code:

def test_set_email(get_all_info_mock):
    # ...
    mock_object = unittest.mock.Mock(Employee)

    actual_email = Employee.set_email(mock_object)

    assert actual_email == expected_email

When running the test I get the following error.

AttributeError: Mock object has no attribute 'id'

I tried to follow the directions here: Better way to mock class attribute in python unit test . I've also tried to set the mock as a property mock, id witha side_effect, and id with a return_value but I can't seem to figure it out. I don't want to patch the Employee class because the goal is to test it's methods.

Answer 1

All you need to do is set the id attribute.

def test_set_email(get_all_info_mock):
    # ...
    mock_object = unittest.mock.Mock(id=3)  # Or whatever id you need

    actual_email = Employee.set_email(mock_object)

    assert actual_email == expected_email