Many .NET framework types, particularly from earlier versions of .NET, aren't implemented in a way that makes the type easy to construct or mock in tests. The same can be said for many third-party libraries that your (legacy) applications may be dependent on upon. To a certain extent this also could apply to your (legacy) code, which in theory could be modified but large changes may be too risky in the time available. For this post I will focus on one particular type that often is the cause of much pain when trying to get code under test, namely System.Data.DataRow