Is it possible to mock an enum with Spock?

Question

I have a switch statement to handle an java enum foo, and am using spock to write some groovy unit tests. I have already added a test which verifies that every type of foo is currently handled without throwing an exception. Now I want to test that an unrecognised type of foo will cause an exception to be thrown.

To do this I will have to mock an enum, and have already seen the solution outlined here: Mocking Java enum to add a value to test fail case

I also know that it is possible to do with powermock, but I really like spock, as I find it incredibly lightweight and so was looking for a solution using spock.

I thought something like this might have worked:

    def "An unexpected type of foo causes an exception to be thrown"() {
        given:
        Foo foo = Mock()
        when:
        subjectUnderTest.handleFoo foo
        then:
        thrown Exception
}

However, this fails with the following error message: org.spockframework.mock.CannotCreateMockException: Cannot create mock for class com.Foo because Java mocks cannot mock final classes. If the code under test is written in Groovy, use a Groovy mock.

I was wondering if anybody knew of a way to do this using spock, as I can't find a solution on any documentation.

Edit After some of the comments below, I feel it is best to clarify why I want to write these tests.

I work in a team with quite a few developers, and it is quite possible that one of them will update the enum. I want tests to fail if this happens to make the developer aware that they need to add logic to handle the new enum type. For this, I wrote a test that iterates over every possible value that the enum could have, passed it into the method and verify that no exception is thrown. Now, if a user added a new enum, this test would fail as there is nothing to handle it so an exception would (hopefully) be thrown.

The second test (the one I am struggling to write) is to clarify that the default logic works as I would expect it to, and that an exception does in fact get thrown. The only way I can think of doing this without creating an enum value that I will never want to be used is to mock an enum, and test that an exception gets thrown if the enum value is not handled.

The code looks like this:

Enum Foo:

public enum Foo {
    ONE, TWO;
}

Method to handle foo:

private void handleFoo(Foo foo) {
    switch (foo) {
        case ONE:
           doEventOne();
           break;
        case TWO:
           doEventTwo()
           break;
        default:
           throw new IllegalArgumentException("Do not know how to handle " + foo);
}

Answer 1

The following specification will cover adding new enum without providing service logic for it:

def 'no exception thrown for all enums'() {
    given:
    def service = new SampleService()

    when:
    service.handleFoo(se)

    then:
    noExceptionThrown()

    where:
    se << SampleEnum.values()
}

I've tried to write a test that will mock the enum or add another value in test runtime, however failed for now. Will back to it later on.

Spock doesn't support mocking enums.