Uniform
Uniformly shards test cases given a total number of shards. For instrumentation tests, it will be translated to "-e numShard" and "-e shardIndex" AndroidJUnitRunner arguments. With uniform sharding enabled, specifying either of these sharding arguments via environment_variables is invalid. Based on the sharding mechanism AndroidJUnitRunner uses, there is no guarantee that test cases will be distributed uniformly across all shards.
Properties
The total number of shards to create. This must always be a positive number that is no greater than the total number of test cases. When you select one or more physical devices, the number of shards must be <= 50. When you select one or more ARM virtual devices, it must be <= 100. When you select only x86 virtual devices, it must be <= 500.