[file-diet] Refactor TerminalTestReporter.Summary.cs (715 lines) into focused partial files

[github-actions]

Overview

The file src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/TerminalTestReporter.Summary.cs has grown to 715 lines, making it harder to navigate and maintain. This task involves refactoring it into smaller, more focused partial-class files — consistent with how the rest of TerminalTestReporter is already organized.

Current State

• File: src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/TerminalTestReporter.Summary.cs
• Size: 715 lines
• Language: C#

Structural Analysis

The file is a partial class on TerminalTestReporter and contains three distinct concerns:

1. Test-run summary (lines 13–521): AppendTestRunSummary, AppendSlowestTests, AppendSlowestTestLine, AppendFlakyTests, AppendFlakyTestLine, AppendRetrySummaryLines. These methods render the post-run verdict including pass/fail/skip counts, slowest-tests ranking, and retry/flaky-test details.

2. Discovery summary (lines 234–349): TestDiscovered (two overloads) and AppendTestDiscoverySummary. These methods handle the test-discovery mode output path, which is conceptually separate from execution output.

3. Coverage summary (lines 523–715): AppendCoverageSummary (public and private overloads), FormatThresholdPercentages, GetCoverageScopeLabel, GetCoverageMetricLabel, GetCoverageThresholdLabel, GetCoverageAggregationLabel, GetCoverageScopeLevelLabel. This block renders code-coverage results and threshold pass/fail results; it is self-contained and already the largest logical section.

Refactoring Strategy

Proposed File Splits

The TerminalTestReporter.Summary.cs file should be split along existing logical boundaries into three focused files:

1. TerminalTestReporter.Summary.cs (retained, trimmed)

   • Contents: AppendTestRunSummary, AppendSlowestTests, AppendSlowestTestLine, AppendFlakyTests, AppendFlakyTestLine, AppendRetrySummaryLines
   • Responsibility: Render the post-execution run summary (verdict, counts, slowest/flaky tests, retry details)
   • Estimated size: ~340 lines

2. TerminalTestReporter.Discovery.cs (new file)

   • Contents: TestDiscovered (both overloads), AppendTestDiscoverySummary
   • Responsibility: Handle test-discovery mode output — tracking discovered tests and rendering the discovery summary
   • Estimated size: ~120 lines

3. TerminalTestReporter.Coverage.cs (new file)

   • Contents: AppendCoverageSummary (public + private), FormatThresholdPercentages, GetCoverageScopeLabel, GetCoverageMetricLabel, GetCoverageThresholdLabel, GetCoverageAggregationLabel, GetCoverageScopeLevelLabel
   • Responsibility: Render code-coverage summary and threshold results
   • Estimated size: ~200 lines

Implementation Guidelines

1. Preserve Behavior: All existing functionality must work identically after the split
2. Maintain Public API: internal and public members stay accessible with the same names (partial class guarantees this)
3. Test After Each Split: Run the unit and acceptance test suites after each incremental file move
4. One File at a Time: Move the coverage block first (self-contained), then discovery, leaving the trimmed summary last
5. No new using directives needed: All three new files share the same using set as today

Acceptance Criteria

• TerminalTestReporter.Summary.cs is split into focused partial files
• Each new file is under 350 lines
• All unit tests pass after refactoring (./build.sh -test / .\build.cmd -test)
• No breaking changes to public or internal API
• File naming follows the existing TerminalTestReporter.<Concern>.cs convention

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Priority: Medium
Effort: Small
Expected Impact: Improved code navigability, easier focused review, reduced merge conflicts on this high-churn file

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• expires on Aug 2, 2026, 7:19 PM UTC