[perf-improver] Replace Array.IndexOf(GetType()) with 'is' pattern matching in hot paths

[Evangelink]

Goal and Rationale

Every test node update passes through TestApplicationResult.ConsumeAsync — including the common InProgressTestNodeStateProperty transitions that fire for every test start/end. The previous code had a switch statement that already dispatched on all known types, then re-ran GetType() plus up to three Array.IndexOf scans (4–5 elements each) to increment counters and classify outcomes. This double-dispatch was pure overhead.

Two other hot paths — AbortForMaxFailedTestsExtension (active when --maximum-failed-tests is set) and RetryDataConsumer (active when retry is on) — had the same pattern.

Approach

Replace every Array.IndexOf(WellKnownTestNodeXxx, state.GetType()) != -1 idiom with an is FailedTestNodeStateProperty or ErrorTestNodeStateProperty ... type-pattern chain, which is resolved by the JIT into a sequence of isinst/type-check instructions with no allocation, no dictionary lookup, and no array traversal.

In TestApplicationResult.ConsumeAsync, the counter increments (_failedTestsCount++, _totalRanTests++) were merged directly into the existing switch arms, removing the redundant second pass entirely.

Files changed:

File	Change
TestApplicationResult.cs	Fold counters into switch; remove GetType() + 3× Array.IndexOf
AbortForMaxFailedTestsExtension.cs	Replace 1× GetType() + Array.IndexOf with is pattern
RetryDataConsumer.cs	Replace 2× GetType() + Array.IndexOf with is patterns

Performance Evidence

The change is a mechanical substitution of array-scan classification with JIT-inlined isinst checks. For a 10 000-test run:

• Before: ConsumeAsync called ~10 000× — each call boxed GetType() then scanned arrays of 4–5 Type objects up to 3 times.
• After: counters are updated in the same switch branch that was already dispatching; no extra allocations.

No microbenchmark exists in this repo for this path yet; the improvement is verified by code-path analysis. The WellKnownTestNodeXxx arrays remain in TestNodeProperties.Categories.cs for documentation and any callers outside this hot path.

Trade-offs

• Very small increase in code verbosity vs. array reference (explicit type list in each condition). Acceptable since the list is short and stable.
• No semantic changes — the classification logic is identical.

Reproducibility

./build.sh
.dotnet/dotnet run --project test/UnitTests/Microsoft.Testing.Platform.UnitTests -f net9.0 --no-build
.dotnet/dotnet run --project test/UnitTests/Microsoft.Testing.Extensions.UnitTests -f net9.0 --no-build

Test Status

Build: ✅ succeeded (0 warnings, 0 errors)
Microsoft.Testing.Platform.UnitTests: ✅ 1220 passed, 0 failed
Microsoft.Testing.Extensions.UnitTests: ✅ 539 passed, 0 failed

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[Copilot]

Pull request overview

This PR removes redundant GetType() + Array.IndexOf(...) outcome classification in several high-frequency data consumers, replacing it with direct type-pattern matching and folding counter updates into existing switch dispatch. The intent is to reduce per-test overhead on hot paths in Microsoft.Testing.Platform and its Retry extension.

Changes:

• Fold _failedTestsCount / _totalRanTests updates directly into the existing switch (executionState) in TestApplicationResult.ConsumeAsync, eliminating the second classification pass.
• Replace Array.IndexOf(..., state.GetType()) with is ... or ... type patterns in AbortForMaxFailedTestsExtension and RetryDataConsumer.
• Preserve the existing “skipped tests do not count as ran” behavior by keeping skipped excluded from _totalRanTests.

Show a summary per file

File	Description
src/Platform/Microsoft.Testing.Platform/Services/TestApplicationResult.cs	Removes post-switch array-scan classification; updates counters in the same switch arms that already handle each state.
src/Platform/Microsoft.Testing.Platform/Extensions/AbortForMaxFailedTestsExtension.cs	Replaces failure-type array membership check with explicit type-pattern matching before incrementing fail count / triggering stop policy.
src/Platform/Microsoft.Testing.Extensions.Retry/RetryDataConsumer.cs	Replaces outcome/failure array membership checks with explicit type-pattern matching for retry signaling and total test counting.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 0