Unit testing

For those seeking instant gratification

Maciej Bliziński <blizinski@google.com>Python Ireland 2010-11-10

Helps the designProvides live documentationHelps refactoring

But I'm hungry right now!

I love to see my code run

task: Index a list of dictionaries by one of the fields

def IndexBy(d_list, field_name): result = {} for d in d_list: result[d[field_name]] = d return result

def MakePackageNameBySoname(soname): """Find the package name based on the soname.

Returns a pair of pkgname, catalogname. """ def AddSeparator(d, sep): """Adds a separator based on the neighboring of two digits.""" dc = copy.copy(d) if dc["version"]: if (dc["basename"][-1].isdigit() and dc["version"][0].isdigit()): dc["sep"] = sep else: dc["sep"] = "" else: dc["sep"] = "" return dc soname_re = re.compile(r"(?P<basename>[\w\+]+([\.\-]+[\w\+]+)*)" r"\.so" r"(\.(?P<version>[\d\.]+))?" r"$") m = soname_re.match(soname) if not m: # There was no ".so" component, so it's hardo to figure out which one is # the name, but we'll try to figure out the numeric part of the soname. digits = "".join(re.findall(r"[0-9]+", soname)) alnum = "".join(re.findall(r"[a-zA-Z]+", soname)) parsed = { "basename": alnum, "version": digits, } else: parsed = m.groupdict() keywords_pkgname = {} keywords_catalogname = {}

(continued...)

for key in parsed: if parsed[key]: keywords_pkgname[key] = SonameToStringWithChar(parsed[key], "-") keywords_catalogname[key] = SonameToStringWithChar(parsed[key], "_") else: keywords_pkgname[key] = "" keywords_catalogname[key] = "" pkgname_list = [] keywords_pkgname = AddSeparator(keywords_pkgname, "-") pkgname_list.append( "CSW%(basename)s%(sep)s%(version)s" % keywords_pkgname) keywords_catalogname = AddSeparator(keywords_catalogname, "_") catalogname_list = [ "%(basename)s%(sep)s%(version)s" % keywords_catalogname, ] return pkgname_list, catalogname_list

Real life example

task: Index a list of dictionaries by one of the fields

def IndexBy(d_list, field_name): result = {} for d in d_list: result[d[field_name]] = d return result

import example_1

def main(): d = [{"foo": "a", "bar": "b"}, {"foo": "c", "bar": "d"}] print example_1.IndexBy(d, "foo")

if __name__ == '__main__': main()

import unittestimport example_1import pprint

class IndexByUnitTest(unittest.TestCase):

def testTwoElements(self): d = [{"foo": "a", "bar": "b"}, {"foo": "c", "bar": "d"}] pprint.pprint(example_1.IndexBy(d, "foo"))

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

import unittestimport example_1

class IndexByUnitTest(unittest.TestCase):

def testTwoElements(self): d = [{"foo": "a", "bar": "b"}, {"foo": "c", "bar": "d"}] expected = { 'a': {'foo': 'a', 'bar': 'b'}, 'c': {'foo': 'c', 'bar': 'd'}, } self.assertEquals(expected, example_1.IndexBy(d, "foo"))

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

blizinski@workstation ~/unit-test-talk $ python2.6 example_1_test.py .----------------------------------------------------------------------Ran 1 test in 0.000s

OK

Cultured way of playing with code

Changing your code

import unittestimport example_1

class IndexByUnitTest(unittest.TestCase):

def testTwoElements(self): d = [{"foo": "a", "bar": "b"}, {"foo": "c", "bar": "d"}, {"foo": "c", "bar": "e"}] expected = { 'a': {'foo': 'a', 'bar': 'b'}, 'c': {'foo': 'c', 'bar': 'd'}, } self.assertEquals(expected, example_1.IndexBy(d, "foo"))

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

task: Index a list of dictionaries by one of the fields

def IndexBy(d_list, field_name): result = {} for d in d_list: result.setdefault(d[field_name], []) result[d[field_name]].append(d) return result

Keeping a track record

def testMakePackageNameDashesNoDashes(self): soname = "libpyglib-2.0-python.so.0" expected = ( ['CSWlibpyglib2-0python0'], ['libpyglib2_0python0'], ) self.assertEqual(expected, su.MakePackageNameBySoname(soname))

def testMakePackageNameDashesNoDashesPython(self): soname = "libpython3.1.so.1.0" expected = ( ['CSWlibpython3-1-1-0'], ['libpython3_1_1_0'], ) self.assertEqual(expected, su.MakePackageNameBySoname(soname))

The trust issue

Your first steps in unit testing

Hug me, I only look alien!(never mind my boxing gloves)

It's about the waypieces of code

fit together

Your trust will gradually shift

Part of the development process

It's a tool which helps with some of the everyday tasks.

Further reading

http://en.wikipedia.org/wiki/Unit_testinghttp://diveintopython.org/unit_testing/index.htmlMock objects, stubs and fakes

ContactMaciej Bliziński <blizinski@google.com>

References

Images:

http://commons.wikimedia.org/wiki/File:Pantheon_rome_inside_1-muniu.jpg by Muniuhttp://commons.wikimedia.org/wiki/File:Instant_miso_soup.jpg by Gleamhttp://www.flickr.com/photos/f-oxymoron/4203860207/sizes/l/in/photostream/ by f-oxymoronhttp://www.flickr.com/photos/jurvetson/1381322008/sizes/l/in/photostream/ by jurvetsonhttp://www.flickr.com/photos/7332902@N05/3221210836/ by David O'Driscollhttp://www.flickr.com/photos/edsweeney/4212380812/sizes/o/in/photostream/ by Ed Sweeney

http://www.flickr.com/photos/jenny-pics/3230153121/sizes/l/in/photostream/ by jenny downinghttp://www.flickr.com/photos/oskay/265899766/ by Windell Oskayhttp://www.flickr.com/photos/alismith44/357361903/ by Ali Westhttp://www.flickr.com/photos/cezaryborysiuk/3947857278/ by Cezary Borysiukhttp://www.flickr.com/photos/wilhei/109403331/ by wilhei55http://www.flickr.com/photos/antonymayfield/3221876089/ by antony_mayfieldhttp://www.flickr.com/photos/ralphandjenny/4999895776/ by Ralph Daily