unit testing - Mock static method with GroovyMock or similar in Spock

Question

First-timer here, apologies if I've missed anything. I'm hoping to get around a call to a static method using Spock. Feedback would be great

With groovy mocks, I thought I'd be able to get past the static call but haven't found it. For background, I'm in the process of retrofitting tests in legacy java. Refactoring is prohibited. I'm using spock-0.7 with groovy-1.8.

The call to the static method is chained with an instance call in this form:

public class ClassUnderTest{

public void methodUnderTest(Parameter param){
  //everything else commented out
Thing someThing = ClassWithStatic.staticMethodThatReturnsAnInstance().instanceMethod(param);
   }

}

staticMethod returns an instance of ClassWithStatic instanceMethod returns the Thing needed in the rest of the method

If I directly exercise the global mock, it returns the mocked instance ok:

def exerciseTheStaticMock(){
    given:
    def globalMock = GroovyMock(ClassWithStatic,global: true)
    def instanceMock = Mock(ClassWithStatic)

    when:
    println(ClassWithStatic.staticMethodThatReturnsAnInstance().instanceMethod(testParam))

    then:
    interaction{
        1 * ClassWithStatic.staticMethodThatReturnsAnInstance() >> instanceMock
        1 * instanceMock.instanceMethod(_) >> returnThing
    }
}

But if I run the methodUnderTest from the ClassUnderTest:

def failingAttemptToGetPastStatic(){
    given:
    def globalMock = GroovyMock(ClassWithStatic,global: true)
    def instanceMock = Mock(ClassWithStatic)
    ClassUnderTest myClassUnderTest = new ClassUnderTest()

    when:
    myClassUnderTest.methodUnderTest(testParam)

    then:
    interaction{
        1 * ClassWithStatic.staticMethodThatReturnsAnInstance() >> instanceMock
        1 * instanceMock.instanceMethod(_) >> returnThing
    }
}

It throws down a real instance of ClassWithStatic that goes on to fail in its instanceMethod.

Answer 1

Spock can only mock static methods implemented in Groovy. For mocking static methods implemented in Java, you'll need to use a tool like GroovyMock , PowerMock or JMockit.

PS: Given that these tools pull of some deep tricks in order to achieve their goals, I'd be interested to hear if and how well they work together with tests implemented in Groovy/Spock (rather than Java/JUnit).