when:
        def cachedClasspath = transformer.transform(classpath, transform)

        then:
        cachedClasspath.asFiles == [cachedFile]

        and:
        1 * transform.applyConfigurationTo(_) >> { Hasher hasher -> hasher.putInt(123) }
        1 * transform.apply(_, _, _) >> { entry, visitor, data ->
            assert entry.name == "a.class"
            Pair.of(entry.path, visitor)
        }

        return target
    }

    private static class NoOpTransformer implements ClassTransform {
        @Override
        void applyConfigurationTo(Hasher hasher) {
        }

        @Override
        Pair<RelativePath, ClassVisitor> apply(ClasspathEntryVisitor.Entry entry, ClassVisitor visitor, ClassData classData) {

        String className = origin.getClassName();
        return classpathTransformer.transform(DefaultClassPath.of(genericClassesDir), new ClassTransform() {
            @Override
            public void applyConfigurationTo(Hasher hasher) {
                hasher.putString(GroovyScriptClassCompiler.class.getSimpleName());
                hasher.putInt(1); // transformation version
                hasher.putString(className);
            }

    private static final String CREATE_CALL_SITE_ARRAY_METHOD = "$createCallSiteArray";

    private final JvmBytecodeInterceptorSet externalInterceptors;

    @Override
    public void applyConfigurationTo(Hasher hasher) {
        hasher.putString(InstrumentingClassTransform.class.getSimpleName());
        hasher.putInt(DECORATION_FORMAT);
    }

    public InstrumentingClassTransform() {