Example

Let's say we have a TagRepository class, which has a fetch_all method on it. This method will fetch all instances of Tag from the database for us. The Tag class looks like this:

class Tag(object):
    def __init__(self, name):
        self.name = name

We also have a class that we'd like to test, called TagDisplayer. Its constructor takes a TagRepository, and has a method display_all. We want to test that this method will grab all of the tags from the repository, sort them into alphabetical order, and write their names into a string, separated by new lines:

from nose.tools import assert_equals
import funk
from funk import expects

@funk.with_context
def test_tag_displayer_writes_all_tag_names_in_alphabetical_order_onto_separate_lines(context):
    tag_repository = context.mock(TagRepository)
    expects(tag_repository).fetch_all(sorted=False).returns([Tag('python'), Tag('debian')])

    tag_displayer = TagDisplayer(tag_repository)
    assert_equals(tag_displayer.display_all(), 'debian\npython')

By using a mock object instead of a real instance of TagRepository, we avoid relying on a correct implementation of TagRepository. We can also run the test without a running database.