Test Sharding {#test-sharding}

Modern CI hosts offer multi-core environments that allow some degree of test parallelization. However, there are scenarios where you need to go beyond what a single host can offer — for example, when you're limited by the number of simulators you can run simultaneously, or when your test suite simply outgrows a single machine.

In those cases, you need a system that distributes tests across multiple CI runners and aggregates the results back into a unified view. That's what test sharding does.

Tuist uses historical test timing data to intelligently balance the load across shards using a bin-packing algorithm, so each runner finishes at roughly the same time. Results from all shards are automatically aggregated in <.localized_link href="/guides/features/test-insights">Test Insights</.localized_link>, giving you a single unified view of your test suite across all shards.

<HomeCards> <HomeCard icon="" title="Xcode" details="Shard Xcode tests across parallel CI runners." linkText="Xcode test sharding" link="/guides/features/test-sharding/xcode"/> <HomeCard icon="" title="Generated projects" details="Shard tests in Tuist generated projects across parallel CI runners." linkText="Generated projects test sharding" link="/guides/features/test-sharding/generated-projects"/> <HomeCard icon="" title="Gradle" details="Shard Gradle tests across parallel CI runners." linkText="Gradle test sharding" link="/guides/features/test-sharding/gradle"/> </HomeCards>

[!WARNING] Requirements

• A <.localized_link href="/guides/server/accounts-and-projects">Tuist account and project</.localized_link>
• <.localized_link href="/guides/features/test-insights">Test Insights</.localized_link> configured (for optimal shard balancing based on historical timing data)