Is it possible to have a global setup method in Spock test?

We ended up doing the following. First we defined a class implementing IAnnotationDrivenExtension interface:

class MockConfigMapExtension implements IAnnotationDrivenExtension<MockConfigMap> {

    @Override
    void visitSpecAnnotation(MockConfigMap annotation, SpecInfo spec) {
        // WRITE THE RELEVANT STARTUP CODE HERE
    }

    @Override
    void visitFeatureAnnotation(MockConfigMap annotation, FeatureInfo feature) {
    }

    @Override
    void visitFixtureAnnotation(MockConfigMap annotation, MethodInfo fixtureMethod) {
    }

    @Override
    void visitFieldAnnotation(MockConfigMap annotation, FieldInfo field) {
    }

    @Override
    void visitSpec(SpecInfo spec) {
    }
}

where we defined this trivial annotation:

@Retention(RetentionPolicy.RUNTIME)
@Target([ElementType.TYPE])
@ExtensionAnnotation(MockConfigMapExtension.class)
@interface MockConfigMap {
}

Now, whenever we annotate a Spec class with the MockConfigMap annotation, the visitSpecAnnotation method is invoked, and we get the desired behaviour.