Stubbing instanceOf

[Patricio Arvizu]

Hi,

Is there a way to stub interactions with the instanceof operator in
Java?

I have something like:

public class SystemUnderTestTest
{
public void test()
{
MyClass mockMyClass = mock(MyClass.class);
SystemUnderTest sut = new SystemUnderTest();
sut.foo(mockMyClass);
}
}

public class SystemUnderTest
{
public void foo(IMyClass myClass)
{
if (myClass instanceof MyClass)
{
//Do something
}
else
{
//Throw exception
}
}
}

Thanks!

[szczepiq]

Hi,

>Is there a way to stub interactions with the instanceof operator in
>Java?

Sure. Create an object or a mock of X type and the instanceof will
pass. Create an object or a mock of Y type and the instanceof will
fail. That's all you need really to be able to describe the behavior
of your class in the test.

Cheers,
Szczepan Faber

[Patricio Arvizu]

I don't have access to my source code right now but I'm pretty sure I
tried and it was not as simple as that.

When I created a mock of MyClass, calls to instanceof MyClass would
return false, since the mock's type was something like "MyClass
$EnhancedByMockito219781723" or at least that's what the Eclipse
debugger showed.

Is there a way to get around this? How does instanceof work
internally? Does it call getClass()? Would it be a good idea to stub
this method?

Thanks!
-Patricio

[szczepiq]

Hi,

Have a look at javadoc on instanceof:
http://java.sun.com/javase/6/docs/api/java/lang/Class.html#isInstance(java.lang.Object)

Then you might try this in your code:

List mock = mock(List.class);
assertTrue(mock instanceof List);

Hope this helps,
Cheers,
Szczepan Faber

[Patricio Arvizu]

I was mocking the wrong interface... duh.

Thanks for your answers anyway.

On 13 jun, 16:21, szczepiq <szcze...@gmail.com> wrote:
> Hi,
>

> Have a look at javadoc on instanceof:http://java.sun.com/javase/6/docs/api/java/lang/Class.html#isInstance...)

>
> Then you might try this in your code:
>
> List mock = mock(List.class);
> assertTrue(mock instanceof List);
>
> Hope this helps,
> Cheers,
> Szczepan Faber
>