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How to parallelise .NET tests

.NET tests run serially and take twenty minutes.

5 min read

.NET tests run serially and take twenty minutes.

Why it happens

xUnit parallelises within an assembly by default but not across them, and CI often runs one assembly at a time.

How to fix it

  1. Run dotnet test with --parallel and multiple test projects at once
  2. Split test projects across a matrix for very large suites
  3. Check for shared state — parallelism exposes tests that were never isolated

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