Module partition

Support for partitioning test runs across several machines.

At the moment this only supports simple hash-based and count-based sharding. In the future it could potentially be made smarter: e.g. using data to pick different sets of binaries and tests to run, with an aim to minimize total build and test times.

Enums

• PartitionerBuilder
  A builder for creating Partitioner instances.

Traits

• Partitioner
  Represents an individual partitioner, typically scoped to a test binary.