public void PrependMessage_UnknownType() { try { throw new NullReferenceException(Original); } catch (Exception e) { var e2 = e.PrependMessage(Prepended); AssertAll.Of( e2, Is.Not.Null, Is.TypeOf <NullReferenceException>(), Is.InstanceOf <NullReferenceException>(), Is.AssignableTo <NullReferenceException>(), Has.Property(nameof(e.Message)).StartsWith(Prepended), Has.Property(nameof(e.Message)).EndsWith(Original) ); } }