Using spocks method counter on mocks out of compositions? - unit-testing

Question

I have an issue with creating test data with spock framework.
To follow "composition over inheritance", I have a class to create testdata for my unit tests. As a simple snipped it looks like this:
class TestData extends Specification{
Foo createFoo(){
GroovyMock(Foo){
doSomething() >> "MOCKED!"
}
}
}
When I write a Test, i like to test, if and how often the method has been invoked. Like this
def "simple test"(){
given:
TestData testData = new TestData()
Foo foo = testData.createFoo()
when:
println foo.doSomething()
then:
1 * foo.doSomething()
}
I know, this test doesn't makes sense. It's just for illustriating the behavior.
I would expect a "green result" of that test, since doSomething() has been invoked 1 time. But test result is red:
Too few invocations for:
1 * foo.doSomething() (0 invocations)
[...]
When i mock Foo directly, everything works fine :
def "simple test"(){
given:
Foo foo = GroovyMock(Foo){
doSomething() >> "MOCKED!"
}
when:
println foo.doSomething()
then:
1 * foo.doSomething()
}
Anyone has an idea how to treat this without deriving my testclass from TestData?
Btw. I used the stub returning "MOCKED!" to show, the mock works. But its not "overwritten" or whatever it is called, when testData created the mock.

Answer 1

Mocks interactions must be defined inside the Specification that uses them. Importing mocks from other sources like
TestData testData = new TestData()
Foo foo = testData.createFoo()
is not supported.
While it is possible to create mocks outside of a Specification and attach them later on, it is not possible to define interactions outside of a Specification.