anchor.diff:        String key;
   
         setUp(() {
  -        ref = database.ref("notes");
  +        ref = database.ref("messages");
           key = ref.push({"text": "hello"}).key;
           expect(key, isNotNull);
         });
  
positive.code:       test("parent", () {
          var childRef = ref.child("text");
          expect(childRef, isNotNull);
          expect(childRef.parent.toString(), "${databaseUrl}/notes");
        });
  
        test("root", () {
          var childRef = ref.child("text");
          expect(childRef.root.toString(), contains(databaseUrl));
        });
      });
    });
  }
  
negative.code:       tearDown(() async {
          await ref.remove();
          ref = null;
          key = null;
        });
  
        test("child and once on value", () async {
          var childRef = ref.child(key);
          var event = await childRef.once("value");
          expect(event.snapshot.key, key);
          expect(event.snapshot.val()["text"], "hello");
  
          childRef = childRef.child("text");
          event = await childRef.once("value");
          expect(event.snapshot.key, "text");
          expect(event.snapshot.val(), "hello");
        });
  
        test("key", () {
  