Add ILLink conditional test scope to reduce PR validation time

CODEOWNERS

@@ -93,12 +93,11 @@
 /test/TemplateEngine @dotnet/templating-engine-maintainers
 /template_feed @dotnet/templating-engine-maintainers
 
-# ILLink and ReadyToRun targets and tasks owned by runtime team
 # Area-ILLink Area-ReadyToRun
-/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.ILLink.targets @dotnet/illink
-/test/Microsoft.NET.Publish.Tests/GivenThatWeWantToRunILLink.cs @dotnet/illink
+/test/Microsoft.NET.ILLink.Tests @dotnet/illink
 # Publish.targets related to ILLink and ReadyToRun is own by both runtime and SDK team
 /src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Publish.targets @dotnet/illink @dotnet/dotnet-cli
+
 # Area-ClickOnce
 /src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.ClickOnce.targets @sujitnayak
 

documentation/project-docs/pr-test-filtering.md

@@ -66,8 +66,8 @@ project(s) (e.g. TemplateEngine tests).
 
 Individual test classes are excluded via `[TestCategory]` attributes and MSTest filter
 expressions. The test project still runs on Helix, but specific classes are skipped.
-This is useful when expensive tests (e.g. ILLink trimming tests) live in a shared test
-assembly alongside cheaper tests. Not yet implemented.
+This is useful when expensive tests live in a shared test assembly alongside cheaper
+tests. Not yet implemented.
 
 ### Method-level filtering (future)
 
@@ -174,10 +174,30 @@ also trigger its tests. For example:
   `src/Cli/Microsoft.DotNet.Cli.Definitions/**`.
 - Shared infrastructure or utility projects that multiple features depend on may need to
   appear in multiple scopes' trigger paths.
-- Test assets (e.g. `test/TestAssets/TestPackages/`) that a test suite consumes at
-  runtime should also be included. These are easy to overlook because they are not
-  referenced via `ProjectReference`, but changes to them can cause test failures just
-  the same.
+- Test assets (e.g. `test/TestAssets/TestProjects/`, `test/TestAssets/TestPackages/`)
+  that a test suite consumes at runtime should also be included. These are easy to
+  overlook because they are not referenced via `ProjectReference` — they are looked up
+  by name at test runtime via `TestAssetsManager.CopyTestAsset("AssetName")`. A change
+  to a test asset can silently break tests even when no source file in the scope's
+  `TriggerPaths` has changed.
+
+  **How to find them**: search the test files for string literals passed to
+  `CopyTestAsset`, `GetTestAsset`, or similar helpers. Any asset name found in
+  `test/TestAssets/TestProjects/` or `test/TestAssets/TestPackages/` that is unique to
+  (or primarily used by) this test suite should be added as an explicit trigger path
+  (e.g. `test/TestAssets/TestProjects/MyAsset/**`). For broadly shared assets
+  used across dozens of unrelated test suites (e.g. `HelloWorld`), use judgment
+  — whether to include them is a trade-off between trigger precision and the risk
+  that a shared asset change breaks this suite without activating any other scope
+  that would otherwise catch the regression.
+
+**Runtime behavior vs. compile-time dependencies**: not all dependencies need to be in
+trigger paths. Ask whether a change to that dependency could cause a test to silently
+*pass when it should fail*. If yes, it is a runtime behavior dependency and belongs in
+`TriggerPaths`. If a change would instead cause a *compilation failure* (e.g. a shared
+constants file, a resx, a helper primarily used for test parameterization such as `[DynamicData]`),
+it is a compile-time dependency and does not need to be listed — the build will fail
+loudly before any tests run, making the gap immediately visible.
 
 Use judgment here. If a feature has complex or far-reaching dependencies that make it
 difficult to define a reliable set of trigger paths, it may not be a good candidate for

sdk.slnx

@@ -374,8 +374,9 @@
     <Project Path="test/Microsoft.NET.Build.Containers.IntegrationTests/Microsoft.NET.Build.Containers.IntegrationTests.csproj" />
     <Project Path="test/Microsoft.NET.Build.Containers.UnitTests/Microsoft.NET.Build.Containers.UnitTests.csproj" />
     <Project Path="test/Microsoft.NET.Build.Tests/Microsoft.NET.Build.Tests.csproj" />
-    <Project Path="test/Microsoft.NET.Infrastructure.Tests/Microsoft.NET.Infrastructure.Tests.csproj" />
     <Project Path="test/Microsoft.NET.Clean.Tests/Microsoft.NET.Clean.Tests.csproj" />
+    <Project Path="test/Microsoft.NET.ILLink.Tests/Microsoft.NET.ILLink.Tests.csproj" />
+    <Project Path="test/Microsoft.NET.Infrastructure.Tests/Microsoft.NET.Infrastructure.Tests.csproj" />
     <Project Path="test/Microsoft.NET.Pack.Tests/Microsoft.NET.Pack.Tests.csproj" />
     <Project Path="test/Microsoft.NET.Publish.Tests/Microsoft.NET.Publish.Tests.csproj" />
     <Project Path="test/Microsoft.NET.Rebuild.Tests/Microsoft.NET.Rebuild.Tests.csproj" />

src/Tasks/Microsoft.NET.slnf

@@ -41,6 +41,7 @@
       "test\\Microsoft.Extensions.DotNetDeltaApplier.Tests\\Microsoft.Extensions.DotNetDeltaApplier.Tests.csproj",
       "test\\Microsoft.NET.Build.Tests\\Microsoft.NET.Build.Tests.csproj",
       "test\\Microsoft.NET.Clean.Tests\\Microsoft.NET.Clean.Tests.csproj",
+      "test\\Microsoft.NET.ILLink.Tests\\Microsoft.NET.ILLink.Tests.csproj",
       "test\\Microsoft.NET.Pack.Tests\\Microsoft.NET.Pack.Tests.csproj",
       "test\\Microsoft.NET.Publish.Tests\\Microsoft.NET.Publish.Tests.csproj",
       "test\\Microsoft.NET.Rebuild.Tests\\Microsoft.NET.Rebuild.Tests.csproj",

test/ConditionalTests.props

@@ -57,6 +57,18 @@
       <RunAlways>CI</RunAlways>
     </ConditionalTestScope>
 
+    <ConditionalTestScope Include="ILLink">
+      <Mechanism>project</Mechanism>
+      <TestProjects>test/Microsoft.NET.ILLink.Tests/Microsoft.NET.ILLink.Tests.csproj</TestProjects>
+      <TriggerPaths>
+        src/Tasks/Microsoft.NET.Build.Tasks/**;
+        test/Microsoft.NET.ILLink.Tests/**;
+        test/TestAssets/TestProjects/TrimmableNetstandardLibrary/**;
+        test/TestAssets/TestProjects/TrimmedAppWithReferences/**
+      </TriggerPaths>
+      <RunAlways>CI</RunAlways>
+    </ConditionalTestScope>
+
     <ConditionalTestScope Include="NetAnalyzers">
       <Mechanism>project</Mechanism>
       <TestProjects>src/Microsoft.CodeAnalysis.NetAnalyzers/tests/**/*.csproj</TestProjects>

test/Microsoft.NET.Publish.Tests/GivenThatWeWantToRunILLink.cs → test/Microsoft.NET.ILLink.Tests/GivenThatWeWantToRunILLink.cs

@@ -11,11 +11,12 @@
 using Microsoft.DotNet.Cli.Utils;
 using Microsoft.Extensions.DependencyModel;
 using Microsoft.NET.Build.Tasks;
+using Microsoft.NET.Publish.Tests;
 using Newtonsoft.Json.Linq;
+using static Microsoft.NET.ILLink.Tests.ILLinkTestUtils;
 using static Microsoft.NET.Publish.Tests.PublishTestUtils;
-using static Microsoft.NET.Publish.Tests.ILLinkTestUtils;
 
-namespace Microsoft.NET.Publish.Tests
+namespace Microsoft.NET.ILLink.Tests
 {
     // this test class is split up arbitrarily so Helix can run tests in multiple workitems
     [TestClass]
@@ -184,10 +185,13 @@ public void PublishTrimmed_fails_for_unsupported_target_framework(string targetF
             var testAsset = TestAssetsManager.CreateTestProject(testProject, identifier: targetFramework);
             var publishCommand = new PublishCommand(testAsset);
             var result = publishCommand.Execute($"/p:RuntimeIdentifier={rid}");
-            if (shouldFail) {
+            if (shouldFail)
+            {
                 result.Should().Fail()
                     .And.HaveStdOutContaining($"error {Strings.PublishTrimmedRequiresVersion30}");
-            } else {
+            }
+            else
+            {
                 result.Should().Pass()
                     .And.NotHaveStdOutContaining("warning");
             }
@@ -223,13 +227,16 @@ public void IsTrimmable_warns_when_expected_for_not_correctly_multitargeted_libr
             var buildCommand = new BuildCommand(testAsset);
             var resultAssertion = buildCommand.Execute("/p:CheckEolTargetFramework=false")
                 .Should().Pass();
-            if (shouldWarn) {
+            if (shouldWarn)
+            {
                 resultAssertion
                     // Note: can't check for Strings.IsTrimmableUnsupported because each line of
                     // the message gets prefixed with a file path by MSBuild.
                     .And.HaveStdOutContaining($"warning NETSDK1212")
                     .And.HaveStdOutContaining($"<IsTrimmable Condition=\"$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0'))\">true</IsTrimmable>");
-            } else {
+            }
+            else
+            {
                 resultAssertion.And.NotHaveStdOutContaining($"warning");
             }
         }

test/Microsoft.NET.Publish.Tests/GivenThatWeWantToRunILLink1b.cs → test/Microsoft.NET.ILLink.Tests/GivenThatWeWantToRunILLink1b.cs

@@ -4,10 +4,11 @@
 #nullable disable
 
 using Microsoft.NET.Build.Tasks;
+using Microsoft.NET.Publish.Tests;
+using static Microsoft.NET.ILLink.Tests.ILLinkTestUtils;
 using static Microsoft.NET.Publish.Tests.PublishTestUtils;
-using static Microsoft.NET.Publish.Tests.ILLinkTestUtils;
 
-namespace Microsoft.NET.Publish.Tests
+namespace Microsoft.NET.ILLink.Tests
 {
     // this test class is split up arbitrarily so Helix can run tests in multiple workitems
     [TestClass]

test/Microsoft.NET.Publish.Tests/GivenThatWeWantToRunILLink2b.cs → test/Microsoft.NET.ILLink.Tests/GivenThatWeWantToRunILLink2b.cs

@@ -3,10 +3,11 @@
 
 #nullable disable
 
+using Microsoft.NET.Publish.Tests;
+using static Microsoft.NET.ILLink.Tests.ILLinkTestUtils;
 using static Microsoft.NET.Publish.Tests.PublishTestUtils;
-using static Microsoft.NET.Publish.Tests.ILLinkTestUtils;
 
-namespace Microsoft.NET.Publish.Tests
+namespace Microsoft.NET.ILLink.Tests
 {
     // this test class is split up arbitrarily so Helix can run tests in multiple workitems
     [TestClass]

test/Microsoft.NET.Publish.Tests/GivenThatWeWantToRunILLink3b.cs → test/Microsoft.NET.ILLink.Tests/GivenThatWeWantToRunILLink3b.cs

@@ -3,11 +3,12 @@
 
 #nullable disable
 
+using Microsoft.NET.Publish.Tests;
 using Newtonsoft.Json.Linq;
+using static Microsoft.NET.ILLink.Tests.ILLinkTestUtils;
 using static Microsoft.NET.Publish.Tests.PublishTestUtils;
-using static Microsoft.NET.Publish.Tests.ILLinkTestUtils;
 
-namespace Microsoft.NET.Publish.Tests
+namespace Microsoft.NET.ILLink.Tests
 {
     // this test class is split up arbitrarily so Helix can run tests in multiple workitems
     [TestClass]

test/Microsoft.NET.ILLink.Tests/Microsoft.NET.ILLink.Tests.csproj

@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project Sdk="MSTest.Sdk">
+
+  <PropertyGroup>
+    <EnableDefaultItems>false</EnableDefaultItems>
+    <OutDirName>Tests\$(MSBuildProjectName)</OutDirName>
+    <PackageId>testSdkILLink</PackageId>
+    <TargetFramework>$(SdkTargetFramework)</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="System.Reflection.MetadataLoadContext" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Microsoft.NET.TestFramework.MSTest\Microsoft.NET.TestFramework.MSTest.csproj" />
+    <ProjectReference Include="..\TelemetryStdOutLogger\TelemetryStdOutLogger.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Compile Include="**\*.cs" Exclude="$(GlobalExclude)" />
+    <Compile Include="..\Microsoft.NET.Publish.Tests\PublishTestUtils.cs" LinkBase="Shared" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <EmbeddedResource Include="..\..\src\Tasks\Common\Resources\Strings.resx" LinkBase="Resources" GenerateSource="True" Namespace="Microsoft.NET.Build.Tasks" />
+    <PackageReference Include="Microsoft.DotNet.XliffTasks" Version="$(MicrosoftDotNetXliffTasksPackageVersion)" PrivateAssets="all" IsImplicitlyDefined="true" />
+  </ItemGroup>
+
+</Project>