jit-regression-test

# JIT Regression Test Extraction > 🚨 **Do NOT create a test when**: the issue has no reproducible code and you cannot compose a minimal repro, the issue is a duplicate of an existing JIT regression test, or the bug is in libraries/runtime rather than the JIT compiler itself. Extract a JIT regression test case from a GitHub issue into a properly structured test under `src/tests/JIT/Regression_*/`. ## Step 1: Gather Information from the GitHub Issue From the GitHub issue, extract: 1. **Issue number** → folder/file name (e.g., #99391 → `Runtime_99391`) 2. **Reproduction code** — if none provided, compose a minimal repro yourself 3. **Environment variables** — any `DOTNET_*` vars needed to reproduce 4. **Expected behavior** — correct output/behavior ## Step 2: Choose the Test Location For a simple test using optimized compilation without debug information, add the source file directly to: ``` src/tests/JIT/Regression_ro_2/Runtime_<issue_number>.cs ``` `Regression_ro_2/Regression_ro_2.csproj` recursively includes sources in its directory. Do not edit its source list or create a project for the test. Use a `Runtime_<issue_number>/` subdirectory only when keeping multiple related files together. If the test needs its own project (see Step 4), use a separate directory outside the globbed source directories: ``` src/tests/JIT/Regression_2/Runtime_<issue_number>/ ``` ## Step 3: Create the Test File Create a `Runtime_<issue_number>.cs` file following these conventions: Example: ```csharp // Licensed to the .NET Foundation under one or more agreements. // The .NET Foundation licenses this file to you under the MIT license. using System; using System.Runtime.CompilerServices; using Xunit; public class Runtime_<issue_number> { [Fact] public static void TestEntryPoint() { // Test code that exercises the bug // Use Assert.Equal, Assert.True, etc. for validation } } ``` ### Key Conventions - **License header**: Always include the standard .NET Foundation license header - **Class name**: Match the file name exactly (`Runtime_<issue_number>`) - **Test method**: `[Fact]` attribute, named `TestEntryPoint()` - **Minimize the reproduction**: Strip to the minimal case that triggers the bug - **Use `[MethodImpl(MethodImplOptions.NoInlining)]`** when preventing inlining is needed to reproduce ### Example: Simple Test (from Runtime_99391) ```csharp // Licensed to the .NET Foundation under one or more agreements. // The .NET Foundation licenses this file to you under the MIT license. namespace Runtime_99391; using System; using System.Runtime.CompilerServices; using System.Numerics; using Xunit; public class Runtime_99391 { [Fact] public static void TestEntryPoint() { Vector2 result2a = Vector2.Normalize(Value2); Assert.Equal(new Vector2(0, 1), result2a); } private static Vector2 Value2 { [MethodImpl(MethodImplOptions.NoInlining)] get => new Vector2(0, 2); } } ``` ## Step 4: Create a .csproj File Only When Required A custom `.csproj` file is **only required** when: - Environment variables are needed to reproduce the bug (such as `DOTNET_JitStressModeNames`) - Special compilation settings are required - Separate assemblies, native dependencies, or process isolation are required Otherwise, the source glob in `Regression_ro_2.csproj` includes the test automatically. Keep custom projects and their sources under `src/tests/JIT/Regression_2/Runtime_<issue_number>/`. `Regression_2/Regression_2.csproj` discovers those projects recursively without compiling their sources directly. Do not place them in source-glob directories such as `src/tests/JIT/Regression_ro_2/`, where they would also be compiled with the runner's settings. If a custom .csproj file is needed, it should be located next to the test source file with the following name: `Runtime_<issue_number>.csproj`. Example: ```xml <Project Sdk="Microsoft.NET.Sdk"> <PropertyGroup> <Optimize>True</Optimize> <DebugType>None</DebugType> <!-- Needed for CLRTestEnvironmentVariable --> <RequiresProcessIsolation>true</RequiresProcessIsolation> </PropertyGroup> <ItemGroup> <Compile Include="$(MSBuildProjectName).cs" /> <CLRTestEnvironmentVariable Include="DOTNET_TieredCompilation" Value="0" /> </ItemGroup> </Project> ``` ## Tips - **No .csproj edits needed for simple tests** — add the `.cs` file under `src/tests/JIT/Regression_ro_2/`. - **Look at recent tests** under `src/tests/JIT/Regression_ro_2/` for simple tests, or `src/tests/JIT/Regression_2/Runtime_*` for tests with custom projects.