We used ArgumentNullException in these cases because it describes the cause more precisely than a NullReferenceException and has build in support for the parameter name.
I'd accept both as a valid response to a null in any tests. Usually we don't bother with null tests in cases when a dereference would throw NPE immediately.
We used ArgumentNullException in these cases because it describes the cause more precisely than a NullReferenceException and has build in support for the parameter name.