Keynote Systems (KEYN) said Monday that it has agreed to be sold to the private-equity investment firm Thoma Bravo LLC for $395 million in cash.

Keynote, of San Mateo, Calif., sells testing and monitoring services for internet and mobile user interfaces.

It also issues reports on which banks' digital offerings perform best.

Keynote said it expects the deal, subject to regulatory and Keynote shareholder approvals, to close before Sept. 30. On the deal's completion Keynote would become privately held.

"We believe becoming a private company will provide additional flexibility and better position us to strategically invest in our nascent mobile enterprise business, further our sales programs and accelerate the next stage of the company's growth and industry market leadership," Umang Gupta, Keynote's chairman and chief executive, said in a press release.

Senior management is expected to remain with the company and Keynote is expected to remain in San Mateo.