public void OnePropertyValueShouldBeAppended(PropertyValueCollection collection) { // Fixture setup collection.SetValue(DirectoryProperty.Member, DN.Parse(john)); // Exercise system collection.AppendValue(DirectoryProperty.Member, DN.Parse(paul)); // Verify outcome collection.GetValues <DN>(DirectoryProperty.Member) .Should().BeEquivalentTo(DN.Parse(john), DN.Parse(paul)); }