auger-python 0.1.27

Automatically generate unit tests for Python code

Auger

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

See these slides or this blog entry for more information.

Installation

Install auger with:

pip install auger-python

Running Auger

To generate a unit test for any class or module, run your sample code using Auger as follows:

import auger

with auger.magic([ <any list of modules or classes> ]):
    <any code that exercises your application>

A Simple Example

Here is a simple example that does not rely on Auger at all:

class Foo:                # Declare a class with a method
    def bar(self, x):
        return 2 * x .    # Duplicate x and return it

def main():
    foo = Foo()           # Create an instance of Foo
    print(foo.bar(32))    # Call the bar method and print the result

main()

Inside the main function we call the method and verifies it prints 64.

Running Auger on our Simple Example

To generate a unit test for this class, we run the code again, but this time in the context of Auger:

import auger

with auger.magic([Foo]):
    main()

This will print out the following:

64
Auger: generated test: tests/test_Foo.py

The test that is generated looks like this, with some imports and test for main removed:

import unittest

class FooTest(unittest.TestCase):
    def test_bar(self):
        foo_instance = Foo()
        self.assertEquals(
            foo_instance.bar(x=32),
            64
        )

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

Running Auger in verbose mode

Rather than emit tests in the file system, Auger can also print out the test to the console. Use the following parameter:

import auger

with auger.magic([Foo], verbose=True):
    main()

A larger example

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]):   # this is the new line and invokes Auger
    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.