Derive a class in your test from the base class. In derived class create a method that calls base class's method. Now you can instantiate the test class, I'll do a property example (just to make you work and do the same for the method, as you haven't posted your code :) )
//this could be created in your unit tests proj public class MyBaseClassExtended : MyBaseClass { public MyBaseClassExtended () : base() { } public new object SomeProperty { get { return base.SomeProperty; } } //now I can test [Test] public void Test() { var x= new MyBaseClassExtended (); Assert.IsNotNull(x.SomeProperty);