public static boolean isSpec(Class<?> clazz) {
    return clazz.isAnnotationPresent(SpecMetadata.class);
  }
Tells if the given class is a Spock specification. Might return <tt>false</tt>
even though the class implements <tt>spock.lang.Specification</tt>. This can
happen if the class wasn't compiled properly (i.e. Spock's AST transform wasn't run).
spock-core/src/main/java/org/spockframework/runtime/SpecUtil.java