Keynote Systems (KEYN) SC 13D KEYNOTE SYSTEMS / Discovery Group I ownership change

EXHIBIT 2

JOINT FILING AGREEMENT

 The undersigned hereby agree to the joint filing of the Schedule 13D to which this Agreement is attached.

Dated:  May 4, 2012

DISCOVERY GROUP I, LLC
By:	/s/ Michael R. Murphy*
	Michael R. Murphy Managing Member

Daniel J. Donoghue*
Daniel J. Donoghue*
Michael R. Murphy*
Michael R. Murphy
By:	/s/ Mark Buckley
	Mark Buckley
	Attorney-in-Fact for Daniel J. Donoghue
	Attorney-in-Fact for Michael R. Murphy