Python Test inheritance with multiple subclasses

Question

I would like to write a Python test suite in a way that allows me to inherit from a single TestBaseClass and subclass it multiple times, everytime changing some small detail in its member variables.

Something like:

import unittest

class TestBaseClass(unittest.TestCase):

  def setUp(self):
    self.var1 = "exampleone"

class DetailedTestOne(TestBaseClass):
  def setUp(self):
    self.var2 = "exampletwo"

  def runTest(self):
    self.assertEqual(self.var1, "exampleone")
    self.assertEqual(self.var2, "exampletwo")

class DetailedTestOneA(DetailedTestOne):
  def setUp(self):
    self.var3 = "examplethree"

  def runTest(self):
    self.assertEqual(self.var1, "exampleone")
    self.assertEqual(self.var2, "exampletwo")
    self.assertEqual(self.var3, "examplethree")

... continue to subclass at wish ...

In this example, DetailedTestOne inherits from TestBaseClass and DetailedTestOneA inherits from DetailedTestOne.

With the code above, I get:

AttributeError: 'DetailedTestOne' object has no attribute 'var1'

for DetailedTestOne and:

AttributeError: 'DetailedTestOneA' object has no attribute 'var1'

for DetailedTestOneA

Of course, var1, var2, var3 could be some members of a same variable declared in first instance in the TestBaseClass.

Any ideas on how to achieve such behaviour?

BrenBarn · Accepted Answer · 2015-10-24 22:30:38Z

3

You need to call the superclass implementation in your subclasses by doing, e.g., super(DetailedTestOne, self).setUp() from inside your DetailedTestOne.setUp method.

answered Oct 24, 2015 at 22:30

BrenBarn

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2 Comments

Francis Straccia Over a year ago

Perfect! I thought the test framework would nest setUp calls for me treating it as an __init__, but I was wrong.

BrenBarn Over a year ago

@FrancisStraccia: Nothing special about __init__ in this regard. If your subclass overrides __init__ and you want the superclass __init__ to be called, you have to call it explicitly in the same way I showed here.

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