chore: import upstream snapshot with attribution

tests/fixtures/sample.groovy

@@ -0,0 +1,35 @@
+package com.nicklastrange.example
+
+import com.nicklastrange.Processor
+import com.nicklastrange.util.Helper
+
+class SampleService {
+    Processor processor
+
+    SampleService(Processor processor) {
+        this.processor = processor
+    }
+
+    String process(String input) {
+        def result = processor.transform(input)
+        return Helper.clean(result)
+    }
+
+    private void reset() {
+        processor.reset()
+    }
+}
+
+interface Resettable {
+    void reset()
+}
+
+class ExtendedService extends SampleService implements Resettable {
+    ExtendedService(Processor processor) {
+        super(processor)
+    }
+
+    void reset() {
+        // no-op
+    }
+}