Question

I’ve got a unittest test file containing four test classes each of which is responsible for running tests on one specific class. Each test class makes us of exactly the same set-up and teardown methods. The set-up method is relatively large, initiating about 20 different variables, while the teardown method simply resets these twenty variables to their initial state.

Up to now I have been putting the twenty variables in each of the four setUp classes. This works, but is not very easily maintained; if I decide to change one variable, I must change it in all four setUp methods. My search for a more elegant solution has failed however. Ideally I’d just like to enter my twenty variables once, call them up in each of my four setup methods, then tear them down after each of my test methods. With this end in mind I tried putting the variables in a separate module and importing this in each setUp, but of course the variables are then only available in the setup method (plus, though I couldn’t put my finger on the exact reasons, this felt like a potentially problem-prone way of doing it

from unittest import TestCase

class Test_Books(TestCase):
    def setup():
        # a quick and easy way of making my variables available at the class level
        # without typing them all in

    def test_method_1(self):
        # setup variables available here in their original state
        # ... mess about with the variables ...
        # reset variables to original state

    def test_method_2(self):
        # setup variables available here in their original state
        # etc...

    def teardown(self):
        # reset variables to original state without having to type them all in



class Books():
    def method_1(self):
        pass

    def method_2(self):
        pass

Answer 1

An alternative is to put the twenty variables into a separate class, set the values in the class’s __init__ and then access the data as class.variable, thus the only place to set the variable s in the __init__ and the code s not duplicated.

class Data:
    def __init__(self):
        data.x= ...
        data.y = ....

class Test_Books(TestCase):
    def setup():
        self.data = Data()

    def test_method_1(self):
       value = self.data.x   # get the data from the variable

This solution makes more sense if the twenty pieces of data are related to each other. Also if you have twenty pieces of data I would expect them to be related and so they should be combined in the real code not just in test.