Mock final class in Spock

Question

Can spock mock final classes? If so, how? Search results brought up this gist, which would seem to imply so, but I can't find any examples of doing so. I've also found forum posts that say mocking final classes isn't supported.

Solution 1

This specification:

@Grab('org.spockframework:spock-core:1.0-groovy-2.4')
@Grab('cglib:cglib-nodep:3.1')

import spock.lang.*

class Test extends Specification {
    def 'lol'() {
        given: 
        def s = Mock(String) {
            size() >> 10
        }

        expect:
        s.size() == 10        
    }
}

ends with the following exception:

JUnit 4 Runner, Tests: 1, Failures: 1, Time: 29 Test Failure:
lol(Test) org.spockframework.mock.CannotCreateMockException:
Cannot create mock for class java.lang.String because Java mocks cannot mock final classes.
If the code under test is written in Groovy, use Groovy mock.

The solution is to use GroovyMock:

@Grab('org.spockframework:spock-core:1.0-groovy-2.4')
@Grab('cglib:cglib-nodep:3.1')

import spock.lang.*

class Test extends Specification {
    def 'lol'() {
        given: 
        def s = GroovyMock(String) {
            size() >> 10
        }

        expect:
        s.size() == 10        
    }
}

Which works well.

Solution 2

There is a third-party library https://github.com/joke/spock-mockable that seems to do the job. Not sure why it's not so popular.

Comments

[cjstehno]

Sometimes, with Groovy it's best to just give it a try.

[Julian A.]

@cjstehno I tried, and got an exception. But I figured maybe there's a special way of doing it that I don't know about.

[Maximiliano De Lorenzo]

The short answer is no, there is an open issue about that. github.com/spockframework/spock/issues/735

[Julian A.]

Could the difference with String.length() be because it's defined on the Java String class, not the Groovy version? This answer seems to suggest so.

[mike rodent]

@JulianA. This is my experience too: GroovyMock seems to be no help with most Java class final methods. I'd like some clarfication on this... !

[ptk]

Is there any other option other than using GroovyMock? Does Spock provide any other workaround for this problem?