Is it possible to create a mock object that implements multiple interfaces with EasyMock?
Solution 1
EasyMock doesn't support this so you're stuck with fallback of the temporary interface.
As an aside, I smell a little bit of a code wiff - should a method really be treating an object as 2 different things, the Foo
and Closeable
interface in this case?
This implies to me that the method is performing multiple operations and while I suspect one of those operations is to 'close' the Closeable
, wouldn't it make more sense for the calling code to decide whether or not the 'close' is required?
Structuring the code this way keeps the 'open' and 'close' in the same try ... finally
block and IMHO makes the code more readable not to mention the method more general and allows you to pass objects that only implement Foo
.
Solution 2
Although I fundamentally agree with Nick Holt's answer, I thought I should point out that mockito allows to do what you ask with the following call :
Foo mock = Mockito.mock(Foo.class, withSettings().extraInterfaces(Bar.class));
Obviously you'll have to use the cast: (Bar)mock
when you need to use the mock as a Bar
but that cast will not throw ClassCastException
Here is an example that is a bit more complete, albeit totally absurd:
import static org.junit.Assert.fail;
import org.junit.Test;
import static org.mockito.Mockito.*;
import org.mockito.Mockito;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.*;
import org.hamcrest.Matchers;
import java.util.Iterator;
public class NonsensicalTest {
@Test
public void testRunnableIterator() {
// This test passes.
final Runnable runnable =
mock(Runnable.class, withSettings().extraInterfaces(Iterator.class));
final Iterator iterator = (Iterator) runnable;
when(iterator.next()).thenReturn("a", 2);
doThrow(new IllegalStateException()).when(runnable).run();
assertThat(iterator.next(), is(Matchers.<Object>equalTo("a")));
try {
runnable.run();
fail();
}
catch (IllegalStateException e) {
}
}
Solution 3
have you considered something like:
interface Bar extends Foo, Closeable {
}
and then mock interface Bar?
Solution 4
An alternative of the most voted answer still based on Mockito but with annotations. You can set the extraInterfaces
directly from the Mock
annotation as next:
@RunWith(MockitoJUnitRunner.class)
public class MyTest {
@Mock(extraInterfaces = Closeable.class)
private Foo foo;
...
}
NB: extraInterfaces
is of type Class<?>[]
so you can specify several interfaces if needed.
If you need to mock method calls of the extra interfaces you will need to cast your mock. For example let's say that I want to throw an IOException
when I call close()
on my mock foo
, the corresponding code would then be:
Mockito.doThrow(IOException.class).when((Closeable) foo).close();
Solution 5
Another way to solve this problem is to use a CGLib mixin:
final Interface1 interface1 = mockery.mock(Interface1.class);
final Interface2 interface2 = mockery.mock(Interface2.class);
service.setDependence(Mixin.create(new Object[]{ interface1, interface2 }));
mockery.checking(new Expectations(){{
oneOf(interface1).doSomething();
oneOf(interface2).doNothing();
}});
service.execute();
Whether or not this is a good idea, it's something up to discussion...
Daniel Fortunov
Daniel Fortunov holds a First-Class BSc Honours degree in Applied Computer Science and Cybernetics from the University of Reading, where he was awarded the Usher/Whitfield Cybernetics Prize for Best BSc/BEng Degree Result and travelled to New York to present original research at the IEEE EMBS conference. He currently works in London as a software developer in the financial sector.
Updated on December 05, 2020Comments
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Daniel Fortunov over 3 years
Is it possible to create a mock object that implements several interfaces with EasyMock?
For example, interface
Foo
and interfaceCloseable
?In Rhino Mocks you can provide multiple interfaces when creating a mock object, but EasyMock's
createMock()
method only takes one type.Is it possbile to achieve this with EasyMock, without resorting to the fallback of creating a temporary interface that extends both
Foo
andCloseable
, and then mocking that?