concept Bla {
  new Ref<Bla> ref;
}

svoid test_cset_with_Ref() {
  // unlisted concepts do not have backRefs
  
  Bla a = unlisted Bla();
  Bla b = unlisted Bla();
  cset(a, ref := b);
  assertSame(a.ref!, b);
  assertEqualsVerbose(ll(), findBackRefs Bla(b));
  
  new Concepts cc;
  // test with registered concepts
  a = cnew(cc, Bla);
  b = cnew(cc, Bla);
  cset(a, ref := b);
  assertSame(a.ref!, b);
  assertEqualsVerbose(ll(a), findBackRefs Bla(b));

  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
  
  cset(a, ref2 := b);
  assertSame(cget ref2(a), b);
  assertEqualsVerbose(ll(a), findBackRefs Bla(b));
  cset(a, ref2 := null);
  assertNull(cget ref2(a));
  assertEqualsVerbose(ll(), findBackRefs Bla(b)); // test that back ref is gone
}