Python. Unit Test Generation

Only the lazy one has not yet written about the need to write tests. But let's be honest - writing tests is often boring. Especially for legacy code. Hundreds of duplicate, monotonous lines. Boredom. What can be done with this?


^{Picture to attract attention. Beautiful python, yes? (Author of the photo: Paweł Stefaniak)}

Pythoscope

Fortunately, we are programmers - people are lazy, ready to kill a couple of weeks in order to solve an hourly task in five minutes. So in a few minutes of googling in Yandex, I found colleagues in misfortune and an interesting solution to facilitate the writing of tests.

Install Pythoscope:
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sudo pip install Pythoscope 

Test cat

To test a cat, we first actually need a cat. We write it:

 # cat.py class Cat(object): def __init__(self, name='Tom'): self.name = name def eat(self, food): if food == 'fish': return 'Yummy!' else: return 'Ugh!' 

Now go to the folder with cat.py and initialize Pythoscope:

 pythoscope --init 

The command will create a .pythoscope folder where all information related to Pythoscope is stored. And now, finally, the generation of the actual tests:

 pythoscope cat.py 

We have the tests folder with the cat_test.py attached. In which ... There is almost nothing:

 # tests/cat_test.py import unittest class TestCat(unittest.TestCase): def test___init__(self): # cat = Cat(name) assert False # TODO: implement your test here def test_eat(self): # cat = Cat(name) # self.assertEqual(expected, cat.eat(food)) assert False # TODO: implement your test here if __name__ == '__main__': unittest.main() 

Not much? Well, at least now there is a framework that will save us time when writing tests.
As it turned out, there is no magic - the tests themselves will not be written. But all is not lost, we can help Pythoscope understand what to run for tests. For this purpose, the so-called “entry points” (points of entry) are real — some use-case uses of our code.

Let's write the points of entry for our cat:

 # .pythoscope/points-of-entry/eat_fish_poe.py from cat import Cat Cat().eat('fish') 

Run the test generation again:

 pythoscope cat.py 

Now, better, a method has been added to the test class that is actually testing something:

 # tests/cat_test.py ... def test_eat_returns_Yummy_for_fish_after_creation_with_Tom(self): cat = Cat('Tom') self.assertEqual('Yummy!', cat.eat('fish')) ... 

And what if you slip a kote not a fish? Mistake? It is necessary to check this:

 # .pythoscope/points-of-entry/eat_tomato_poe.py from cat import Cat Cat().eat('tomato') 

We generate:

 pythoscope cat.py 

Great, it remains only to check:

 nosetests .. ---------------------------------------------------------------------- Ran 2 tests in 0.001s OK 

Excellent! Successful and easy testing!