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[efficiency-improver] perf: cache MethodInfo.GetParameters() to avoid per-row array allocations in data-driven tests#9514

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Merged
Amaury Levé (Evangelink) merged 2 commits into from
Jun 30, 2026
Merged

[efficiency-improver] perf: cache MethodInfo.GetParameters() to avoid per-row array allocations in data-driven tests #9514

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9d8b54e
perf: cache MethodInfo.GetParameters() to avoid per-row array allocat…
Evangelink Jun 29, 2026
e415e3d
Return fresh array from ITestMethod.ParameterTypes to protect cache
Evangelink Jun 30, 2026
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4 changes: 3 additions & 1 deletion src/Adapter/MSTestAdapter.PlatformServices/Discovery/AssemblyEnumerator.cs
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Expand Up@@ -289,12 +289,14 @@ private static bool TryUnfoldITestDataSource(ITestDataSource dataSource, UnitTes

var discoveredTests = new List<UnitTestElement>();
bool dataSourceHasData = false;
// PERF: Hoist outside the loop — MethodInfo.GetParameters() returns a fresh array copy on each
// call (CLR safety guarantee), so calling it per row allocates N identical arrays for N data rows.
ParameterInfo[] parameters = methodInfo.GetParameters();

foreach (object?[] dataOrTestDataRow in dataEnumerable)
{
dataSourceHasData = true;
object?[] d = dataOrTestDataRow;
ParameterInfo[] parameters = methodInfo.GetParameters();

// The effective ignore message for this row is the row-level ignore message (from
// TestDataRow<T>), falling back to the whole-source ignore message. It must be
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12 changes: 11 additions & 1 deletion src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodInfo.cs
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Expand Up@@ -60,7 +60,17 @@ internal ITestContext TestContext
/// <summary>
/// Gets the parameter types of the test method.
/// </summary>
public ParameterInfo[] ParameterTypes => MethodInfo.GetParameters();
/// <remarks>
/// Lazy-cached: <c>MethodInfo.GetParameters()</c> returns a fresh array copy on every call
/// (CLR safety guarantee), so caching avoids N redundant copies for data-driven tests with N rows.
/// This cached array is shared across internal call sites and MUST NOT be mutated. The explicit
/// <see cref="ITestMethod.ParameterTypes"/> implementation hands external consumers a fresh copy to
/// preserve the previous "fresh array per call" behavior and protect the cache from mutation.
/// </remarks>
public ParameterInfo[] ParameterTypes => field ??= MethodInfo.GetParameters();

/// <inheritdoc />
ParameterInfo[] ITestMethod.ParameterTypes => (ParameterInfo[])ParameterTypes.Clone();

/// <summary>
/// Gets the return type of the test method.
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