Spock @use annotation for partial mocking of CUT

ClassUnderTest.groovy

class ClassUnderTest {

    def index() { }

    def doSomething() {
        return mockMethod('Jojo')
    }

    private def mockMethod(String name) {
        //...something expensive
        return "real method called for $name"
    }

}


class FakeClassUnderTest {

     // we can alos use this as a spy
     static boolean fakeCalled = false

     static mockMethod(ClassUnderTest self, String name) {
        fakeCalled = true
        return "fake mock method called for $name"
    }

}


class ClassUnderTestSpec extends Specification{

    @Use(FakeClassUnderTest)
    def "this is to test the @Use annotation"() {
        given: "we have a new CUT"
            cut = new ClassUnderTest()

        when:"call a method that calls the fake method"
            def result = cut.doSomething()

        then:"check results"
            result == "fake mock method called for Bob"
            FakeClassUnderTest.fakeCalled == true
    }

}