Abstract: Techniques are described for measuring test coverage during phased deployments of software application updates. A phased deployment of a software application update generally involves initially deploying the software update to a subset of compute instances running the software application within a computing environment, using a testing application to verify whether the updated software application is operating as expected, and then deploying the update to the remaining compute instance of the computing environment once the tests are passed. A testing system and framework described herein enables a code deployment service to determine when complete or sufficient test coverage is achieved for software updates deployed in a computing environment supporting a distributed software application.