Overview

The file src/Adapter/MSTestAdapter.PlatformServices/Execution/TypeCache.cs has grown to 1027 lines, making it harder to navigate and maintain. This task involves refactoring it into smaller, more focused files.

Current State

• File: src/Adapter/MSTestAdapter.PlatformServices/Execution/TypeCache.cs
• Size: 1027 lines
• Language: C#

Refactoring Strategy

Because TypeCache is internal sealed, C# partial classes are an idiomatic way to split it without any public-API changes.

Proposed File Splits

1. TypeCache.cs (keep as the primary file)

   • Contents: fields, constructors, public properties, GetTestMethodInfo, GetTestMethodInfoForDiscovery, InitializeLifetimeService
   • Responsibility: Core entry points and state; under ~120 lines after extraction

2. TypeCache.ClassInfo.cs (partial class)

   • Contents: GetClassInfo, CreateTestClassInfo, LoadType, CreateClassInfo, TryGetTimeoutInfo, UpdateInfoIfClassInitializeOrCleanupMethod, UpdateInfoIfTestInitializeOrCleanupMethod
   • Responsibility: Everything related to building and caching TestClassInfo

3. TypeCache.AssemblyInfo.cs (partial class)

   • Contents: GetAssemblyInfo, CreateTestAssemblyInfo, UpdateInfoWithInitializeAndCleanupMethods, IsAssemblyOrClassInitializeMethod, IsAssemblyOrClassCleanupMethod
   • Responsibility: Everything related to building and caching TestAssemblyInfo

4. TypeCache.ProviderDiscovery.cs (partial class)

   • Contents: DiscoverFixturesFromProviders, LoadProviderMarkers, ProcessProviderFixtureType, CollectFixtureMethodsFromProviderType, EnumerateCandidateAssemblies, TryLoadReferencedAssembly, HasAssemblyFixtureProviderMarker, IsFrameworkAssemblyName, SafeGetAssemblyName
   • Responsibility: Assembly fixture-provider scanning (the most self-contained chunk, ~250 lines)

5. TypeCache.MethodResolution.cs (partial class)

   • Contents: ResolveTestMethodInfo, ResolveTestMethodInfoForDiscovery, GetMethodInfoForTestMethod, GetMethodInfoUsingManagedNameHelper
   • Responsibility: Resolving a TestMethod descriptor to a concrete MethodInfo

Implementation Guidelines

1. Preserve Behavior: All existing functionality must work identically after the split
2. Use partial classes: Declare internal sealed partial class TypeCache in every file — no new types, no renames
3. One split at a time: Extract one partial file per commit to keep diffs reviewable
4. Test after each split: Run ./build.sh -test (or .\build.cmd -test) after each step
5. No public-API changes: TypeCache is internal, but keep all internal/public member signatures identical

Acceptance Criteria

• Original file is split into focused partial-class files
• Each new file is under 300 lines
• All tests pass after refactoring (./build.sh -test)
• No breaking changes to any public or internal API
• File names follow the TypeCache.<Concern>.cs convention

Priority: Medium
Effort: Small — the class has no cross-cutting internal state between the proposed groups; splitting into partial files is low-risk
Expected Impact: Improved code navigability, easier testing of individual concerns, reduced merge conflicts

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• expires on Jun 3, 2026, 8:20 PM UTC