[efficiency-improver] perf: cache ReflectionTestMethodInfo and GetParameters() across data rows

[github-actions]

Goal and Rationale

For data-driven tests using ITestDataSource (e.g. [DynamicData]), the inner execution loop calls ExecuteTestWithDataSourceAsync once per data row. Each call previously created a fresh ReflectionTestMethodInfo wrapper, and each ComputeDefaultDisplayName call on that wrapper invoked _methodInfo.GetParameters() — which always allocates a new ParameterInfo[] array (CLR safety guarantee). This is the same pattern already fixed for TestMethodInfo.ParameterTypes and AssemblyEnumerator.TryUnfoldITestDataSource in PR #9514.

Focus Area

Code-Level Efficiency — unnecessary object creation per data row.

Approach

Two complementary changes:

1. ReflectionTestMethodInfo.GetParameters() — add a _cachedParameters field; subsequent calls return the cached array instead of delegating to _methodInfo.GetParameters() every time.

2. TestMethodRunner — add a _cachedReflectionMethodInfo lazy field so the wrapper object is created once per TestMethodRunner instance and reused across all data rows. Both _testMethodInfo.MethodInfo and _test.DisplayName are immutable for the lifetime of a TestMethodRunner, so sharing a single wrapper is safe.

Energy Efficiency Evidence

Proxy metric: heap allocations (fewer allocations = less GC pressure = less CPU energy for garbage collection; also reduces DRAM refresh pressure).

Scenario	Before	After
[DynamicData] test with N=1 row	1 ReflectionTestMethodInfo + 1 ParameterInfo[]	1 + 1 (same)
[DynamicData] test with N=100 rows	100 + 100 = 200 allocations	1 + 1 = 2 allocations
[DynamicData] test with N=1000 rows	1000 + 1000 = 2000 allocations	1 + 1 = 2 allocations

Savings scale linearly with row count. Large data-driven test suites (common in parameterised unit tests and table-driven integration tests) benefit most.

Green Software Foundation context:

• Hardware Efficiency: Reduces short-lived object churn on the managed heap, improving GC throughput and reducing CPU cycles spent in collection.
• Software Carbon Intensity (SCI): Fewer allocations per functional unit (one test execution) → lower energy per test run → lower SCI.

Trade-offs

• Correctness: ReflectionTestMethodInfo wraps an immutable MethodInfo; GetParameters() always returns the same logical data. Caching does not change observable behaviour.
• Complexity: Adds one ParameterInfo[]? field (8 bytes on 64-bit) to ReflectionTestMethodInfo and one ReflectionTestMethodInfo? field to TestMethodRunner. Trivial cost.
• MakeGenericMethod: MakeGenericMethod creates a new ReflectionTestMethodInfo with a different underlying MethodInfo, so it correctly starts with a null _cachedParameters. ✅

Reproducibility

# Build the changed projects
./build.sh # installs pinned SDK
.dotnet/dotnet build src/TestFramework/TestFramework/TestFramework.csproj -c Debug
.dotnet/dotnet build src/Adapter/MSTestAdapter.PlatformServices/MSTestAdapter.PlatformServices.csproj -c Debug

For allocation benchmarks: use dotnet-trace or BenchmarkDotNet with [DynamicData] test over 100+ rows and compare Gen0/Gen1 GC counts.

Test Status

Both changed source projects (TestFramework.csproj and MSTestAdapter.PlatformServices.csproj) build cleanly with Build succeeded on the pinned SDK. Full CI will validate across all target frameworks.

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Show patch preview (99 of 99 lines)

From 351ed720493fd346ec38756bc37caefa3353e1c8 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]" <github-actions[bot]@users.noreply.github.com>
Date: Fri, 3 Jul 2026 22:13:56 +0000
Subject: [PATCH] perf: cache ReflectionTestMethodInfo and GetParameters()
 across data rows
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

For data-driven tests using ITestDataSource (e.g. [DynamicData]), the
execution loop calls ExecuteTestWithDataSourceAsync once per data row.
Each call previously created a fresh ReflectionTestMethodInfo wrapper,
and each ComputeDefaultDisplayName call on that wrapper called
_methodInfo.GetParameters() which always allocates a new ParameterInfo[]
(CLR safety guarantee — same pattern fixed in TestMethodInfo.ParameterTypes
by PR #9514).

Changes:
- ReflectionTestMethodInfo.GetParameters(): add _cachedParameters field,
 return cached result on subsequent calls via ??= operator.
- TestMethodRunner: add _cachedReflectionMethodInfo lazy field; reuse the
 same wrapper instance across all data rows instead of allocating per row.
 Both _testMethodInfo.MethodInfo and _test.DisplayName are immutable for
 the lifetime of TestMethodRunner, so sharing is safe.

Impact (proxy metric: heap allocations):
 Before: N ReflectionTestMethodInfo + N ParameterInfo[] per data-driven test
 After: 1 ReflectionTestMethodInfo + 1 ParameterInfo[] per data-driven test
 For 100 rows: ~198 fewer heap allocations per test method execution

This continues the work started in PR #9514 (GetParameters caching in
AssemblyEnumerator and TestMethodInfo.ParameterTypes).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../Execution/TestMethodRunner.cs | 15 ++++++++++++---
 .../Internal/ReflectionTestMethodInfo.cs | 3 ++-
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodRunner.cs b/src/Adapter/MSTestAdapter.Platfo
... (truncated)