For those not familiar, through Google Play developers can beta test their apps with people who sign up to be testers. The sign up process is simple.
First, you'll want to make sure that you are signed in with the same account that you use for Google Play. Next, click the link below, and opt-in to test. Unlike many other beta tests, for the Google Search app there is no community that you have to join on Google+ to take part. After joining, you will notice an update to the Search app through Google Play becomes available.
Head to below link to become a beta tester
Sign up to beta test Google Search