Test count of association, not class

When testing, you might do something like:

expect { @user.make_widget }.to change { Widget.count }.by(1)

Don't. There might be some reason why the new widget's user_id doesn't get set. Instead, test:

expect { @user.make_widget }.to change { @user.widgets.count }.by(1)

That way you're only looking at the widgets that actually belong to the user.