Summary:
A common util from RN to gate on testing code is `Platform.isTesting()`
Unfortunately, this util does not account for ServerSnapshotTests, since they don't use apple's XCTest infra.
Reviewed By: sahrens
Differential Revision: D13981728
fbshipit-source-id: bf902a04f5d7fcb98a06816f5c2c9b082e7d14b8