Testing in Hard to Reach Places

Lee BeggBegg Digital

Overview

● Goals● The module● Refactoring● SqlAlchemy tricks● Mocking hard things

Code: http://github.com/llnz/kiwipycon2011testingSlides: http://www.beggdigital.com/media/kiwipycon2011testing.pdf

Goals

● Make sure it works properly● All the time● In all conditions

● Unit testing to check● Cover 100%● Might still miss cases

Example moduledef main(): '''Check the tripwire, email if the latest values have an RMS value over 2''' session = model.Session() values = session.query(model.MeasuredValue).order_by(model.MeasuredValue.desc()).limit(20).all() totalsq = 0 for value in values: totalsq += value.value**2 rms = math.sqrt(totalsq) if rms > 2: body = """Database trip wire has been tripped

RMS value was: %s"""

subject = "Tripwire report %s" % datetime.date.today() msg = MIMEText(body) msg['Subject'] = '[DBTW] %s' % subject msg['To'] = ','.join(settings.TO_ADDRESSES) msg['From'] = settings.FROM_ADDRESS server = smtplib.SMTP('localhost') result = server.sendmail(settings.FROM_ADDRESS, settings.TO_ADDRESSES, msg.as_string()) if len(result) != 0: print "sendmail failures: %s" % result server.quit()

Refactoring● Refactor out components to test

def calcRMS(values): totalsq = 0.0 for value in values: totalsq += value**2 rms = math.sqrt(totalsq/len(values)) return rms

class RMSTest(unittest.TestCase): '''Test the RMS calculations''' def testRMSCalc(self): testvalues = [ ([0], 0), ([1], 1), ([2], 2), ([0, 0], 0), ([1, 1], 1), ([0] * 20, 0), ([1] * 20, 1), ([0, 0, 0, 1], 0.5), ([3, 1, 3, 0, 1], 2), ] for values, expected in testvalues: result = tripwire.calcRMS(values) self.assertAlmostEqual(result, expected, msg='rmsCalc(%s) gave %s, expected %s' % (values, result, expected))

SqlAlchemy Tricks

● Change the database in the unittest setUp method

● Done internally by Django

#override database setting

from dbtripwire import settings

settings.DATABASE_URL = 'sqlite:///:memory:'

from dbtripwire.model import initDatabase, dropDatabase

SqlAlchemy Tricks

class DatabaseTestSetup(object): '''Create the database in the setUp, and drop it in tearDown Used to abstract this away from all the unittests that use the Database. Must be the first class inherited from, or TestCase will override these methods, not the other way around. ''' def setUp(self): '''Initialise the database with the tables''' initDatabase()

def tearDown(self): '''Drop the tables''' dropDatabase()

SqlAlchemy Tricksclass ModelTest(DatabaseTestSetup, unittest.TestCase): '''Test the model classes''' def testMeasuredValueTable(self): '''MeasuredValue table test''' session = model.Session() self.assertEqual(session.query(model.MeasuredValue).count(), 0) mv = model.MeasuredValue(5) self.assert_(mv) session.add(mv) session.commit() self.assertEqual(session.query(model.MeasuredValue).count(), 1) mv1 = session.query(model.MeasuredValue).one() self.assertEqual(mv1.id, 1) self.assertEqual(mv1.value, 5) #don't forget to test the __repr__ string self.assertEqual(repr(mv1), "<MeasuredValue(1, 5)>") session.delete(mv1) session.commit() self.assertEqual(session.query(model.MeasuredValue).count(), 0)

Mock

● Creating fake “mock” objects/classes/modules● Replace things you couldn't normally control● A few frameworks available● Very useful in replacing network connections

● Httplib for example● Smtplib for another

Mock exampleclass SendEmailTest(unittest.TestCase): '''Test sending email''' def testSendEmail(self): tt = minimock.TraceTracker() smtpconn = minimock.Mock('smtplib.SMTP', tracker=tt) minimock.mock('smtplib.SMTP', mock_obj=smtpconn) smtpconn.mock_returns = smtpconn smtpconn.sendmail.mock_returns = {} tripwire.sendEmail(2.5, datetime.date(2011, 8, 16)) expected = r"""Called smtplib.SMTP('localhost')Called smtplib.SMTP.sendmail( 'lee@beggdigital.co.nz', ['lee@beggdigital.co.nz', 'llnz@paradise.net.nz'], 'Content-Type: text/plain; charset="us-ascii"\nMIME-Version: 1.0\nContent-Transfer-Encoding: 7bit\nSubject: [DBTW] Tripwire Report 2011-08-16\nTo: lee@beggdigital.co.nz, llnz@paradise.net.nz\nFrom: lee@beggdigital.co.nz\n\nDatabase trip wire has been tripped.\n\nRMS value was: 2.5\n')Called smtplib.SMTP.quit()""" self.assertTrue(tt.check(expected), tt.diff(expected)) minimock.restore()