We know that Python provides a  lot of productivity over any compiled languages. We have programming in C# & need to write the unit test cases in C# itself. If we see the amount of code we write for unit test is approximately ten times more than the original code. 
Is it ideal choice to write unit test cases in IronPython instead of C#? Any body has done like that? I wrote few test cases, they seems to be good. But hairy pointy managers won't accept.
Actually testing is a great opportunity to try integrating a new language. Languages like Python shine especially well in testing, and it's a low risk project to try - the worst case is not too bad at all.
As far as experience testing another language in Python, I've tested C and C++ systems like this and it was excellent. I think it's definitely worth a shot.
What Jon says is true, though - the level of tooling for Python in general, and IronPython in particular, is nowhere near that of C#. How much that affects you is something you'll find out in your pilot.
IronPython For Unit Testing over C#