microsoft/coyote

Health v2 · maintenance only

Flags: no_releases no_license

Adoption not part of the score

1592 stars · 91 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

Coyote is a .NET library and CLI tool from Microsoft Research for systematically testing concurrent C# code and deterministically reproducing concurrency bugs. It uses IL binary rewriting to control scheduling of tasks, actors, and other nondeterminism, exploring many interleavings within ordinary unit tests.

Use cases

• find race conditions in C# code
• test concurrent ASP.NET controllers deterministically
• reproduce flaky concurrency bugs reliably
• systematically explore interleavings of tasks and actors
• test distributed systems logic on a laptop without production environment
• add concurrency unit tests to xUnit test suites

When to choose

• you write concurrent or async C# code and suffer from flaky or hidden race-condition bugs
• you want systematic exploration of schedules instead of stress testing
• you build actor or state-machine based services and want reliable testing
• you need deterministic reproduction of nondeterministic bugs

When to avoid

• your codebase is not on .NET/C#
• you need formal verification or correctness proofs rather than testing
• you only need simple unit tests without concurrency
• you want a language-agnostic fuzzing tool

Facets

library · maturity active

testing fuzzing cli concurrency testing developer-tools microservices dotnet cross-platform cli systematic-testing concurrency-unit-testing binary-rewriting actor-model race-condition-detection csharp

Member repositories

For agents

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