Mocking of a single (native) method?

[sven.s]

Hi,

I'm using EasyMock and have discovered PowerMock because I need to
mock a native (JSNI) method. The problem is that the native method is
included and called within the class which I would like to test. Is it
possible to mock only the single native method so the rest of the code
can be executed. The native method may not be called because an
UnsatisfiedLinkError would occur.

Here is an example code snippet of my class. I want to test the init
method, but the test fails because executeJSNINativeMethod() throws an
UnsatisfiedLinkError when it is called from a testcase. Therefore I
have to mock the native method.

public class MyClass {
public void init() {
//some code is here which should be tested
executeJSNINativeMethod();
//some code is here which should be tested
}

private native void executeJSNINativeMethod() {
//an UnsatisfiedLinkError would occur when this method is called
from a testcase
}
}

Thank you in advance.

Regards,

Sven S.

[Johan Haleby]

Hi Sven,

The best thing to do would probably be to introduce an anti-corruption layer between your code and the native method.  E.g. refactor the method call to its own class and inject an instance of it as a member variable in MyClass. Then it's mockable by vanilla EasyMock. If this is not an option for you then you can use a technique called partial mocking or just suppress the method. In your case you could do something like this:

import static org.powermock.api.support.membermodification.MemberModifier.suppress;
import static org.powermock.api.support.membermodification.MemberMatcher.method;

@RunWith(PowerMockRunner.class)
@PrepareForTest(MyClass.class)
public class MyClassTest  {

    @Test
    public void test() {
        suppress(method(MyClass.class, "executeJSNINativeMethod"));

        // Run your test
        new MyClass().init();
        ..
    }
}

/Johan

[Sven S.]

Hi Johan,

cool, it works! :-) I used the suppress-method to solve the problem.

PowerMock seems to be a great library. Thank you for your support.

Regards,

Sven S.

2010/10/23 Johan Haleby <johan....@gmail.com>

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[Rajesh kumar]

Hi Johan,

I also tried .. Working fine. but Code coverage is Zero %. Please help me coverage as well.

Thanks,

Rajesh