Cristian R. Silvaabout.me/ocristian

Test Doubles

generic term for any kind of pretend object used in place of a real object for testing purposes

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Dummy Object

objects are passed around but never actually used. Usually

they are just used to fill parameter lists

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objects actually have working implementations, but usually take some shortcut which

makes them not suitable for production (an in memory database is a good example).

Fake Object

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provide canned answers to calls made during the test, usually not responding at all to

anything outside what's programmed in for the test. Stubs may also record information

about calls, such as an email gateway stub that remembers the messages it 'sent', or

maybe only how many messages it 'sent'

Stub

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an object with the ability to have a programmed expected behavior, and verify the

interactions occurring in its lifetime (this object is usually created with the help of

mocking framework)

Mock

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a mock created as a proxy to an existing real object; some methods can be stubbed,

while the un- stubbed ones are for- warded to the covered object

Spy

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https://code.google.com/p/mockito/

creating mock objects

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import org.mockito.Mockito;

Person person = Mockito.mock(Person.class);

or

import static org.mockito.Mockito.mock;

Person person = mock(Person.class);

using static method mock()

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using @Mock annotation

@RunWith(MockitoJUnitRunner.class)public class ClassTest {}

or

public class ClassTest{MockitoAnnotations.initMocks(ClassTest.class);

}

creating mock objects

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declaring an attribute with the @Mock annotation

creating mock objects

public class ClassTest {

@Mock private Person person;}

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requesting specific behaviors

Method Description

thenReturn(T valueToBeReturned) returns given value

thenThrow(Throwable toBeThrown)

thenThrow(Class<? extends Throwable> toBeThrown)throws given exception

then(Answer answer)

thenAnswer(Answer answer)uses user created code to answer

thenCallRealMethod() calls real method when working with partial mock/spy

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stubbing method

public class SimpleStubbingTest { public static final int TEST_NUMBER_OF_RELATIVES = 5;

@Test public void shouldReturnGivenValue() {

Person person = mock(Person.class);

when(person.getNumberOfRelatives()).thenReturn(TEST_NUMBER_OF_RELATIVES);

int numberOfRelatives = person.getNumberOfRelatives();assertEquals(numberOfRelatives, TEST_NUMBER_OF_RELATIVES);

}}

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BDDMockito given - when - then

@Test public void shouldReturnGivenValueUsingBDDSemantics() {

// givenPerson person = mock(Person.class);given(person.getNumberOfRelatives()).willReturn(

TEST_NUMBER_OF_RELATIVES);

// whenint numberOfRelatives = person.getNumberOfRelatives();

// thenassertEquals(numberOfRelatives, TEST_NUMBER_OF_RELATIVES);

}

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stubbing multiples calls to the same method

@Test public void shouldReturnLastDefinedValue() {

Weather weather = mock(Weather.class);

given(weather.getTemperature()).willReturn( 10, 12, 23 );

assertEquals(weather.getTemperature(), 10);assertEquals(weather.getTemperature(), 12);assertEquals(weather.getTemperature(), 23);assertEquals(weather.getTemperature(), 23);

}

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stubbing void methods

@Test(expected = WeatherException.class) public void shouldStubVoidMethod() {

Weather weather = mock(Weather.class);

doThrow(WeatherException.class).when(weather).doSelfCheck();

//exception expectedweather.doSelfCheck();

}

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custom answer

public class ReturnCustomAnswer implements Answer<Object> {

public Object answer(InvocationOnMock invocation) throws Throwable {

return null;}

}

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verifying behavior

Method Descriptiontimes(int wantedNumberOfInvocations) called exactly n times (one by default)

never() never called

atLeastOnce() called at least once

atLeast(int minNumberOfInvocations) called at least n times

atMost(int maxNumberOfInvocations) called at most n times

only() the only method called on a mock

timeout(int millis) interacted in a specified time range

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verifying behavior

verify(mockObject, never()).doSelfCheck(); verify(mockObject, times(2)).getNumberOfRelatives(); verify(mockObject, atLeast(1)).getTemperature();

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another verifications

InOrder API verifying the call order

ArgumentCaptor argument matching

timeout verify(mockObject, timeout(10)).getTemperature();

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some limitations

• mock final classes

• mock enums

• mock final methods

• mock static methods

• mock private methods

• mock hashCode() and equals()

will help you!

https://code.google.com/p/powermock/

references

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https://code.google.com/p/mockito/

http://martinfowler.com/articles/mocksArentStubs.html

blog.caelum.com.br/facilitando-seus-testes-de-unidade-no-java-um-pouco-de-mockito/

http://refcardz.dzone.com/refcardz/mockito

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