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Testing in those hard to reach places


KiwiPyCon2011, Wellington, Sunday, Track 1, Testing in those hard to reach places by Lee Begg

KiwiPyCon2011, Wellington, Sunday, Track 1, Testing in those hard to reach places by Lee Begg

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  • 1. Testing in Hard to Reach Places Lee Begg Begg Digital
  • 2. Overview● Goals● The module● Refactoring● SqlAlchemy tricks● Mocking hard things Code: Slides:
  • 3. Goals● Make sure it works properly ● All the time ● In all conditions● Unit testing to check ● Cover 100% ● Might still miss cases
  • 4. Example module def 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 trippedRMS value was: %s""" subject = "Tripwire report %s" % 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()
  • 5. Refactoring● Refactor out components to testclass RMSTest(unittest.TestCase): Test the RMS calculations def testRMSCalc(self): def calcRMS(values): testvalues = [ totalsq = 0.0 ([0], 0), for value in values: ([1], 1), totalsq += value**2 ([2], 2), ([0, 0], 0), rms = math.sqrt(totalsq/len(values)) ([1, 1], 1), return rms ([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))
  • 6. SqlAlchemy Tricks● Change the database in the unittest setUp method● Done internally by Django#override database settingfrom dbtripwire import settingssettings.DATABASE_URL = sqlite:///:memory:from dbtripwire.model import initDatabase, dropDatabase
  • 7. SqlAlchemy Tricksclass 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()
  • 8. 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(, 1) self.assertEqual(mv1.value, 5) #dont 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)
  • 9. Mock● Creating fake “mock” objects/classes/modules● Replace things you couldnt normally control● A few frameworks available● Very useful in replacing network connections ● Httplib for example ● Smtplib for another
  • 10. 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,, 8, 16)) expected = r"""Called smtplib.SMTP(localhost)Called smtplib.SMTP.sendmail(, [,], Content-Type: text/plain; charset="us-ascii"nMIME-Version: 1.0nContent-Transfer-Encoding:7bitnSubject: [DBTW] Tripwire Report 2011-08-16nTo:, trip wire has been tripped.nnRMSvalue was: 2.5n)Called smtplib.SMTP.quit()""" self.assertTrue(tt.check(expected), tt.diff(expected)) minimock.restore()