In the realm of software testing, the challenge of long test suite run times can be mitigated through test splitting, which involves distributing tests across multiple workers to run in parallel. Buildkite's Test Engine Client (bktec) offers a solution to this by enabling efficient parallelization of test suites, thereby reducing the wait time for continuous integration (CI) build results. The client uses historical test timing data and a bin packing algorithm to ensure balanced workload distribution among workers, optimizing for minimal run time while maintaining test isolation and resource allocation. However, it's important to note that the relationship between worker count and execution speed is not linear, with diminishing returns as more workers are added. Factors such as flaky tests can also impact the effectiveness of parallelization, as they may require re-runs that negate performance gains. Furthermore, the Test Engine Client provides features to handle flaky tests by retrying failures and allowing users to mute known flaky tests. The tool currently supports several testing frameworks and is available to Buildkite Pro and Enterprise customers, with an open-source repository for broader accessibility.