public void TestJoinQuery()
{
Person p = new Person();
p.FirstName = "Mirko";
p.LastName = "Matytschak";
p.Moniker = "Hallo";
Adresse a1 = new Adresse();
a1.Lkz = "D";
a1.Plz = "83646";
a1.Straße = "Nockhergasse 7";
a1.Ort = "Bad Tölz";
Adresse a2 = new Adresse();
a2.Ort = "Mönchen";
a2.Plz = "80331";
a2.Straße = "Isartorplatz 5";
a2.Lkz = "D";
Institution i = new Institution();
i.FirstName = "Schnulli";
i.LastName = "Wauwau";
i.Hausmeister = "Möller";
pm.MakePersistent(a1);
pm.MakePersistent(a2);
pm.MakePersistent(p);
pm.MakePersistent(i);
i.AddAdresse(a1);
p.AddAdresse(a1);
p.AddAdresse(a2);
pm.Save();
pm.UnloadCache();
IQuery q = new NDOQuery <Contact>(pm, $"addresses.plz = '{a2.Plz}'");
IList l = q.Execute();
Assert.AreEqual(1, l.Count, "Wrong number of contacts");
}