Automated Unittest Generation for Python
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README.md

auger

Auger is a project to automatically generate unit tests for Python code.

See this blog entry for more information.

Consider the following example, pet.py, that lets us create a Pet with a name and a species:

from animal import Animal

class Pet(Animal):
  def __init__(self, name, species):
    Animal.__init__(self, species)
    self.name = name

  def getName(self):
    return self.name

  def __str__(self):
    return "%s is a %s" % (self.getName(), self.getSpecies())

def createPet(name, species):
  return Pet(name, species)

A Pet is really a special kind of animal, with a name, defined in animal.py.

class Animal(object):
  def __init__(self, species):
    self.species = species

  def getSpecies(self):
    return self.species   

With those two definitions, we can create a Pet and print it out:

import animal
import pet

def main():
  p = pet.createPet("Polly", "Parrot")
  print(p, p.getName(), p.getSpecies())

This produces:

Polly is a Parrot Polly Parrot

With auger, we can record all calls to all functions and methods defined in pet.py, while trapping all calls going out from pet.py to other modules.

Instead of saying:

if __name__ == "__main__":
  main() 

We would say:

import auger
if __name__ == "__main__":
  with auger.magic(pet):
    main() 

This produces the following automatically generated unit test for pet.py:

from mock import patch
from sample.animal import Animal
import sample.pet
from sample.pet import Pet
import unittest


class PetTest(unittest.TestCase):
    @patch.object(Animal, 'get_species')
    @patch.object(Animal, 'get_age')
    def test___str__(self, mock_get_age, mock_get_species):
        mock_get_age.return_value = 12
        mock_get_species.return_value = 'Dog'
        pet_instance = Pet('Clifford', 'Dog', 12)
        self.assertEquals(pet_instance.__str__(), 'Clifford is a dog aged 12')

    def test_create_pet(self):
        self.assertIsInstance(sample.pet.create_pet(age=12,species='Dog',name='Clifford'), Pet)

    def test_get_name(self):
        pet_instance = Pet('Clifford', 'Dog', 12)
        self.assertEquals(pet_instance.get_name(), 'Clifford')

    def test_lower(self):
        self.assertEquals(Pet.lower(s='Dog'), 'dog')

if __name__ == "__main__":
    unittest.main()

Note that auger detects object creation, method invocation, and static methods. As the getSpecies method is defined by the superclass, we mock it out, and make it return 'Parrot', as that is what our test execution produced.

By automatically generating unit tests, we dramatically cut down the cost of software development this way.