Hi,
I'm not sure that I understand the problem.
Do you get a compilation error or error in runtime?
If it's a runtime error please post the test code and the exception message you get including the stack trace.
However if it's a compilation error it seems like a language limitation
For example the code below will not compile.
public class Foo
{ }
public class Bar : Foo
{}
public class UnderTest
{
public void F(Bar bar)
{}
}
[Test, Isolated]
public void Test()
{
var fake = Isolate.Fake.Instance<Foo>();
UnderTest underTest = new UnderTest();
underTest.F(fake); // <-- compilation error here.
}