Slides de la sesión sobre stub, spies & mocks que tuvo lugar en el AOS 2011

1. Test Doubles
Rubén Bernárdez
www.rubenbp.com
@rubenbpv
#aos2011

2. ¿Por qué usamos dobles?
El colaborador:
class Communicator():
def send_email(self, address, total_savings):
suponemos_que_esto_envia_un_email = True
El SUT (System Under Test):
class SavingsService():
def __init__(self, communicator):
self.communicator = communicator
def analyze_month(self, month_savings):
calculation = month_savings[0] + month_savings[1]
self.communicator.send_email('savings@iexpertos.com', calculation)

3. Pruébalo cobarde! … pecador!...
class Communicator():
def send_email(self, address, total_savings):
suponemos_que_esto_envia_un_email = True
class SavingsService():
def __init__(self, communicator):
self.communicator = communicator
def analyze_month(self, month_savings):
calculation = month_savings[0] + month_savings[1]
self.communicator.send_email('savings@iexpertos.com', calculation)
class LoFlipoEnEl_AOS(unittest.TestCase):
def test_report_correcto_es_enviado_a_la_central(self):
communicator = spy(Communicator())
month_savings = [1234,1276435]
service = SavingsService(communicator)
service.analyze_month(month_savings)
assert_that(communicator.send_email).was_called()

4. ¿Mock o Spy?
class LoFlipoEnEl_AOS(unittest.TestCase):
def test_al_menos_es_enviado_a_la_central(self):
communicator = spy(Communicator())
month_savings = [1234,1276435]
service = SavingsService(communicator)
service.analyze_month(month_savings)
assert_that(communicator.send_email).was_called()
def test_se_envia_a_la_central_y_nada_mais(self):
communicator = mock(Communicator())
expect_call(communicator.send_email)
month_savings = [1234,1276435]
service = SavingsService(communicator)
service.analyze_month(month_savings)
communicator.assert_that_is_satisfied()

5. ¿Qué test se romperá?
class Communicator():
def send_email(self, address, total_savings):
suponemos_que_esto_envia_un_email = True
def post_savings(self, total_savings):
suponemos_que_esto_llama_a_un_webservice = True
class SavingsService():
def __init__(self, communicator):
self.communicator = communicator
def analyze_month(self, month_savings):
calculation = month_savings[0] + month_savings[1]
self.communicator.send_email('savings@iexpertos.com', calculation)
self.communicator.post_savings(calculation)

6. Un diseño distinto... ¿Ahora qué hacemos?
class Communicator():
def send_email(self, address, total_savings):
suponemos_que_esto_envia_un_email = True
class AccountRepository():
def month_savings(self):
suponemos_que_esto_devuelve_de_bd_los_ahorros = True
class SavingsService():
def __init__(self, communicator, repository):
self.communicator = communicator
self.repository = repository
def analyze_month(self):
month_savings = self.repository.month_savings()
calculation = month_savings[0] + month_savings[1]
self.communicator.send_email('savings@iexpertos.com', calculation)

7. Mejor Stub que Spy esta vez! fistro!
class SavingsService():
def __init__(self, communicator, repository):
self.communicator = communicator
self.repository = repository
def analyze_month(self):
month_savings = self.repository.month_savings()
calculation = month_savings[0] + month_savings[1]
self.communicator.send_email('savings@iexpertos.com', calculation)
class LoFlipoEnEl_AOS(unittest.TestCase):
def test_si_hay_report_envialo_a_la_central(self):
communicator = spy(Communicator())
repository = stub(AccountRepository())
when(repository.month_savings).then_return([1234,1276435])
service = SavingsService(communicator, repository)
service.analyze_month(month_savings)
assert_that(communicator.send_email).was_called()

8. Tests frágiles VS legibilidad
Classic VS Mockist

9. Test doubles frameworks
 ¿Qué más comportamientos se pueden
programar en los dobles de test? Con qué
frameworks?
 pyDoubles
 Mockito
 Jmock
 Moq
 Rhino.Mocks
 PHPUnit
 GoogleMock

10. pyDoubles.org
Made with TDD and open source!
 when(obj.method).with_args(1).then_return(1000)
 when(obj.method).then_raise(ApplicationException())
 when(obj.method).then_return(1000)
 expect_call(obj.method).with_args(1)
 expect_call(obj.method).with_args(1, ANY_ARG)
 assert_that(obj.method).was_called().with_args(1)
 when(obj.method).with_args(
str_containing(”abc”)).then_return(1)
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11. iExpertos.com
 Formación para equipos de desarrollo:
 Iniciación a TDD y TDD Avanzado
 eXtreme Programming a fondo (XP)
 Coaching
 Desarrollamos contigo:
 Dos iExpertos en tu empresa desde el arranque
del proyecto.
 Formación y desarrollo, todo en uno.