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.

Try mock_object = unittest.mock.Mock(Employee, autospec=True) — rdas
– rdas, Commented Apr 23, 2019 at 16:53
I get the same error. Without the autospec=True when debugging the mock object would look like this <Mock spec='Employee' id='259360400'> — Daniel Butler
– Daniel Butler, Commented Apr 23, 2019 at 17:07
Don't mock the class; that's what you are testing. Mock get_all_info instead and create a real instance of Employee. — chepner
– chepner, Commented Apr 23, 2019 at 17:29
@chepner I'm testing set_email. If I create an instance of the employee class it will call all of the methods in __init__ which is what I am trying to avoid. — Daniel Butler
– Daniel Butler, Commented Apr 23, 2019 at 17:32
Why? If you mock get_all_info to return a static data frame (instead of querying some outside resource, there's no problem with calling set_email. — chepner
– chepner, Commented Apr 23, 2019 at 17:34

chepner · Accepted Answer · 2019-04-23 17:59:31Z

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

answered Apr 23, 2019 at 17:59

chepner

538k77 gold badges594 silver badges746 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Daniel Butler Over a year ago

That is what I was looking for! I went down the path of creating a separate dummy class but this is way better! Thank you for dealing with me in the comments!

Collectives™ on Stack Overflow

Testing class method that calls an instance variable - AttributeError

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related