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Fix O(n²) per-node UID lookup in TestNodeUidListFilter re-run path #7806

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Merged
Evangelink merged 2 commits into from
Apr 24, 2026
Merged

Fix O(n²) per-node UID lookup in TestNodeUidListFilter re-run path #7806

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Copilot Apr 24, 2026
de5ae31
Fix O(n) linear scan in TestNodeUidListFilter by using HashSet for O(…
Copilot Apr 24, 2026
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11 changes: 6 additions & 5 deletions ...blic/TestingPlatformExamples/TestingPlatformExplorer/TestingFramework/TestingFramework.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -142,15 +142,16 @@ public async Task ExecuteRequestAsync(ExecuteRequestContext context)

StringBuilder reportBody = new();
MethodInfo[] tests = GetTestsMethodFromAssemblies();
HashSet<TestNodeUid>? uidFilterSet = runTestExecutionRequest.Filter is TestNodeUidListFilter filter
? [.. filter.TestNodeUids]
: null;
var results = new List<Task>();
foreach (MethodInfo test in tests)
{
if (runTestExecutionRequest.Filter is TestNodeUidListFilter filter)
if (uidFilterSet is not null
&& !uidFilterSet.Contains($"{test.DeclaringType!.FullName}.{test.Name}"))
{
Comment on lines +151 to 153
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Copilot AI Apr 24, 2026

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In this sample, uidFilterSet is a HashSet<TestNodeUid> but Contains is called with an interpolated string, which relies on the implicit string -> TestNodeUid conversion and allocates a new TestNodeUid per check. If you want this to be allocation-free, consider storing uid.Value in a HashSet<string> (e.g., with StringComparer.Ordinal) and comparing against the computed UID string.

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if (!filter.TestNodeUids.Any(testId => testId == $"{test.DeclaringType!.FullName}.{test.Name}"))
{
continue;
}
continue;
}

SkipAttribute? skipAttribute = test.GetCustomAttribute<SkipAttribute>();
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11 changes: 9 additions & 2 deletions src/Adapter/MSTest.Engine/Engine/BFSTestNodeVisitor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,8 @@
using Microsoft.Testing.Platform.Extensions.Messages;
using Microsoft.Testing.Platform.Requests;

using PlatformTestNodeUid = Microsoft.Testing.Platform.Extensions.Messages.TestNodeUid;

namespace Microsoft.Testing.Framework;

internal sealed class BFSTestNodeVisitor
Expand All @@ -32,6 +34,11 @@ public BFSTestNodeVisitor(IEnumerable<TestNode> rootTestNodes, ITestExecutionFil

public async Task VisitAsync(Func<TestNode, TestNodeUid?, Task> onIncludedTestNodeAsync)
{
// Precompute a HashSet for O(1) UID lookups when filtering by UID list.
HashSet<PlatformTestNodeUid>? uidFilterSet = _testExecutionFilter is TestNodeUidListFilter listFilter
? [.. listFilter.TestNodeUids]
: null;

// This is case sensitive, and culture insensitive, to keep UIDs unique, and comparable between different system.
Dictionary<TestNodeUid, List<TestNode>> testNodesByUid = [];
Queue<(TestNode CurrentNode, TestNodeUid? ParentNodeUid, StringBuilder NodeFullPath)> queue = new();
Expand Down Expand Up @@ -81,8 +88,8 @@ public async Task VisitAsync(Func<TestNode, TestNodeUid?, Task> onIncludedTestNo
}

// If the node is not filtered out by the test execution filter, we call the callback with the node.
if (_testExecutionFilter is not TestNodeUidListFilter listFilter
|| listFilter.TestNodeUids.Any(uid => currentNode.StableUid.ToPlatformTestNodeUid() == uid))
if (uidFilterSet is null
|| uidFilterSet.Contains(currentNode.StableUid.ToPlatformTestNodeUid()))
Comment on lines +91 to +92
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Copilot AI Apr 24, 2026

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currentNode.StableUid is already Microsoft.Testing.Platform.Extensions.Messages.TestNodeUid, so calling ToPlatformTestNodeUid() here allocates a new TestNodeUid per visited node. If you want this to be allocation-free (and likely drop the PlatformTestNodeUid alias), you can check uidFilterSet.Contains(currentNode.StableUid) directly.

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{
await onIncludedTestNodeAsync(currentNode, parentNodeUid).ConfigureAwait(false);
}
Expand Down