[efficiency-improver] Single-pass min/max for Azure DevOps result date aggregation

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Goal and rationale

AzureDevOpsResultIdStore.GetEarliestStartedDate/GetLatestCompletedDate (both the public IReadOnlyList<AzureDevOpsTestCaseResult> overload and the internal IReadOnlyList<AzureDevOpsTestSubResult> overload used for attempt history) used attempts.Where(a => a.X is not null).Min/Max(a => a.X). These two methods are always called together from the Azure DevOps live-publishing flush path (AzureDevOpsTestResultsPublisher.ResultPublishing.cs, AzureDevOpsTestResultsPublisher.AttemptPublishing.cs, AzureDevOpsResultIdStore.cs/.Persistence.cs) — i.e. once per batch of published test results/attempts, not a one-time cold path. Each call allocated a Where iterator and enumerated the list twice (once for Min, once for Max).

Focus area

Code-Level Efficiency (redundant enumeration / avoidable LINQ overhead in a per-batch-flush hot path).

Approach

Replaced both LINQ chains with manual single-pass foreach loops that track the running min/max directly — mirroring the existing hand-rolled SumDurations/AddDurations pattern already used right next to these methods in the same file. No behavioral change: null-date entries are still skipped, and an all-null list still returns null.

Energy efficiency evidence

Proxy metrics used: CPU time (Stopwatch) and allocated bytes (GC.GetAllocatedBytesForCurrentThread()) — both map directly to CPU/DRAM energy draw per Green Software Foundation guidance on hardware efficiency.

Standalone (not committed) console benchmark, .NET 8 Release, 2,000,000 call-pairs (GetEarliestStartedDate + GetLatestCompletedDate) over a 5-element list mimicking a typical attempt/sub-result batch:

	Time	Allocated
OLD (Where().Min()/Max())	1073.37 ms	192,000,040 B
NEW (single-pass loop)	511.95 ms	128,000,040 B

~2.1x faster, ~33% less allocation for this call-pair shape. The remaining allocation in both versions comes from DateTimeOffset? boxing in the benchmark harness itself, not from the methods under test.

Green Software Foundation context

• Hardware Efficiency: fewer CPU cycles per flush batch and less GC pressure from eliminated iterator allocations.
• SCI: reduces the Energy term of the SCI equation for the "publish one batch of Azure DevOps test results" functional unit, aggregated across every CI run that uses --report-azdo.

Trade-offs

The loop form is a few lines longer than the one-line LINQ expression, but it directly mirrors the existing SumDurations helper's style already present in the same file, so it doesn't introduce a new pattern to the codebase.

Reproducibility

Benchmark harness (not committed) computed old vs. new implementations side-by-side with warmup iterations before each measured loop; happy to reproduce on request.

Test Status

• ./build.sh (full repo): 0 warnings/errors.
• dotnet build test/UnitTests/Microsoft.Testing.Extensions.UnitTests -f net8.0: 0 warnings/errors.
• Full Microsoft.Testing.Extensions.UnitTests suite (net8.0, run directly): 1839/1839 passed (37 pre-existing skips).
• AzureDevOpsLivePublishingTests-filtered run: 154/154 passed.
• dotnet format whitespace --verify-no-changes on both changed files: clean.

No public API signature changes — both public methods keep their exact signatures, only the internal implementation changed.

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Show patch preview (30 of 103 lines)

From d0a24adf94ca306775e1977d3f4b938017c5b42c Mon Sep 17 00:00:00 2001
X-GH-AW-Base-Commit: 00b4e2a445a42b8768fdd706e7de778e582fb034
From: "github-actions[bot]" <github-actions[bot]@users.noreply.github.com>
Date: Fri, 18 Sep 2026 21:53:47 +0000
Subject: [PATCH] Single-pass min/max for Azure DevOps result date aggregation

Replace Where().Min()/Where().Max() LINQ chains with manual single-pass
loops in AzureDevOpsResultIdStore's GetEarliestStartedDate/GetLatestCompletedDate
(both the public IReadOnlyList<AzureDevOpsTestCaseResult> overload and the
internal IReadOnlyList<AzureDevOpsTestSubResult> overload). These are called
in pairs from the result-flush hot path (once per batch of published test
results/attempts), so the double enumeration + Where iterator allocation was
avoided in favor of the same manual-accumulation pattern already used by the
adjacent SumDurations helper.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 ...AzureDevOpsResultIdStore.AttemptHistory.cs | 26 +++++++++++++++++--
 .../AzureDevOpsResultIdStore.cs               | 26 +++++++++++++++++--
 2 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsResultIdStore.AttemptHistory.cs b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsResultIdStore.AttemptHistory.cs
index 3ae5eda..a03f7e7 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsResultIdStore.AttemptHistory.cs
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsResultIdStore.AttemptHistory.cs
@@ -59,10 +59,32 @@ or AzureDevOpsLivePublishingConstants.NotExecutedTestOutcome
                 : right.Value > long.MaxValue - left.Value ? long.MaxValue : left.Value + right.Value;
 
     private static DateTimeOffset? GetEarliestStartedDate(IReadOnlyList<AzureDevOpsTestSubResult> attempts)
-        => attempts.Where(attempt => attempt.StartedDate is not null).Min(a
... (truncated)

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