concept Bla {

  new Ref<Bla> ref;

}

svoid test_cset_with_Ref() {

  // unlisted concepts do not track back references

  Bla a = unlisted Bla();

  Bla b = unlisted Bla();

  assertEqualsVerbose(1, cset(a, ref := b));

  assertSame(a.ref!, b);

  assertEmptyVerbose(findBackRefs Bla(b));

  new Concepts cc;

  // test with registered concepts

  a = cnew(cc, Bla);

  b = cnew(cc, Bla);

  assertEqualsVerbose(1, cset(a, ref := b));

  assertSame(a.ref!, b);

  assertEqualsVerbose(ll(a), findBackRefs Bla(b));

  assertEqualsVerbose(1, cset(a, ref := null));

  assertNull(a.ref!); // make sure the Ref object itself is not deleted

  assertEqualsVerbose(ll(), findBackRefs Bla(b)); // test that back ref is gone

  // Now test a "dynamic" (undeclared) field

  assertEqualsVerbose(1, cset(a, ref2 := b));

  assertEqualsVerbose(0, cset(a, ref2 := b));

  assertSame(cget ref2(a), b);

  assertEqualsVerbose(ll(a), findBackRefs Bla(b));

  assertEqualsVerbose(1, cset(a, ref2 := null));

  assertEqualsVerbose(0, cset(a, ref2 := null));

  assertNull(cget ref2(a));

  assertEqualsVerbose(ll(), findBackRefs Bla(b)); // test that back ref is gone

  assertEmptyVerbose(ConceptsRefChecker(cc).run());

  // overwrite reference with string 

  assertEqualsVerbose(1, cset(a, ref2 := b));

  assertEqualsVerbose(1, cset(a, ref2 := ""));

  assertEqualsVerbose(0, cset(a, ref2 := ""));

  assertEqualsVerbose(cget(a, "ref2"), "");

  assertEmptyVerbose(ConceptsRefChecker(cc).run());

  // overwrite string with reference

  assertEqualsVerbose(1, cset(a, ref2 := b));

  assertEqualsVerbose(cget(a, "ref2"), b);

  assertEmptyVerbose(ConceptsRefChecker(cc).run());

  // check that a list concepts in dynamic field is converted to RefL

  assertEqualsVerbose(1, cset(b, dynList := ll(a));

  assertEqualsVerbose(0, cset(b, dynList := ll(a));

  Concept.RefL refL = cast getOpt dynList(b);

  assertEqualsVerbose(1, l(refL));

  assertEquals(a, first(refL));

  // TODO: check updating/overwriting RefL

}