[file-diet] Refactor AbortAtDeadlineExtension.cs (600 lines) into focused partial-class files

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Overview

The file src/Platform/Microsoft.Testing.Platform/Extensions/AbortAtDeadlineExtension.cs has grown to 600 lines, making it harder to navigate and maintain. This task involves refactoring it into smaller, more focused files.

Current State

• File: src/Platform/Microsoft.Testing.Platform/Extensions/AbortAtDeadlineExtension.cs
• Size: 600 lines
• Language: C#

Structural Analysis

The file defines a single internal sealed class AbortAtDeadlineExtension that implements IDataConsumer, ITestSessionLifetimeHandler, IOutputDeviceDataProducer, IDisposable (and IAsyncDisposable on .NET Core), plus a private RunState enum. It combines several distinct responsibilities in one type:

• Timer / deadline detection: _timer, OnTimerElapsed, OnDeadlineReached — arming a Timer at construction and reacting when the CI-imposed hard-cancel deadline approaches.
• Graceful-stop orchestration: HandleDeadlineAsync, RequestGracefulStopAsync, ReleaseDeadlineClaim — coordinating with IGracefulStopTestExecutionCapability and IStopPoliciesService to ask the test framework to stop scheduling new tests.
• Lifecycle/session hooks: IsEnabledAsync, NotifyTestExecutionCompleted — implementing ITestSessionLifetimeHandler to detect when the run finished before the timer fires.
• Best-effort diagnostics/reporting: TryReportAsync, TryLog — bounding diagnostic/report calls with a timeout and swallowing/logging failures.
• Disposal: Dispose, DisposeAsync — tearing down the timer and releasing resources, guarded by a _lock to serialize against the timer callback.
• State enum: RunState — tracks whether the deadline handling has not started, is in progress, or has completed.

Refactoring Strategy

Proposed File Splits

Since AbortAtDeadlineExtension is internal sealed, C# partial classes are the safest way to split it without touching its public surface or constructor signature:

1. AbortAtDeadlineExtension.cs (trimmed)

   • Contents: class declaration, interface implementations list, fields, constructor, IsEnabledAsync, NotifyTestExecutionCompleted.
   • Responsibility: Core type definition, construction, and the ITestSessionLifetimeHandler/IDataConsumer entry points.

2. AbortAtDeadlineExtension.DeadlineHandling.cs

   • Contents: OnTimerElapsed, OnDeadlineReached, HandleDeadlineAsync, RequestGracefulStopAsync, ReleaseDeadlineClaim, RunState enum.
   • Responsibility: Timer-driven deadline detection and graceful-stop orchestration logic.

3. AbortAtDeadlineExtension.Diagnostics.cs

   • Contents: TryReportAsync, TryLog.
   • Responsibility: Best-effort, timeout-bounded diagnostic reporting and logging helpers.

4. AbortAtDeadlineExtension.Dispose.cs

   • Contents: Dispose, DisposeAsync.
   • Responsibility: Synchronous and asynchronous teardown, coordinated with the _lock against the timer callback.

Implementation Guidelines

1. Preserve Behavior: All existing functionality must work identically after the split
2. Maintain Public API: Keep exported/public symbols accessible with the same names
3. Update Imports: Fix all import paths throughout the codebase
4. Test After Each Split: Run the test suite after each incremental change
5. One File at a Time: Split one module at a time to make review easier

Acceptance Criteria

• Original file is split into focused modules
• Each new file is under 300 lines
• All tests pass after refactoring
• No breaking changes to public API
• All import paths updated correctly

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Priority: Medium
Effort: Small
Expected Impact: Improved code navigability, easier testing, reduced merge conflicts

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• expires on Sep 23, 2026, 6:57 PM UTC