Daily Test Coverage Improver: Add 13 comprehensive edge case and branch coverage tests

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Summary

Added 13 comprehensive tests targeting previously uncovered edge cases and branch conditions. This improves overall test coverage while ensuring critical boundary conditions and error scenarios are properly validated.

Problems Found

• Edge case coverage gaps: Buffer functions, pairwise, and distinctUntilChanged had minimal testing for boundary conditions
• Exception propagation: Missing tests for error handling in append and concat operations
• Branch coverage: Functions with conditional logic lacked comprehensive testing of all code paths
• Async operation testing: Limited validation of chooseAsync and async transformation scenarios

Actions Taken

Edge Case Tests (6 tests):

• bufferByCount with size 1 should work - Tests single element buffering
• bufferByCount with empty sequence should return empty - Tests empty sequence boundary
• bufferByCount with size larger than sequence should return partial - Tests buffer size larger than input
• pairwise with empty sequence should return empty - Tests empty sequence boundary
• pairwise with single element should return empty - Tests single element boundary
• bufferByCountAndTime with zero time should work - Tests zero timeout edge case

Function Behavior Tests (4 tests):

• distinctUntilChangedWith should work with custom equality - Tests custom equality function with mixed case strings
• distinctUntilChangedWith with all same elements should return single - Tests deduplication behavior
• choose with all None should return empty - Tests filtering that removes all elements
• choose with mixed Some and None should filter correctly - Tests partial filtering behavior

Exception Handling Tests (2 tests):

• append with both sequences having exceptions should propagate first - Tests exception precedence in append
• concat with nested exceptions should propagate properly - Tests exception handling in nested sequences

Async Function Test (1 test):

• chooseAsync with async transformation should work - Tests async transformation and filtering

Changes in Test Coverage Achieved

Before:

• Line Coverage: 86.1% (1,047/1,215 lines)
• Branch Coverage: 71% (182/256 branches)
• Method Coverage: 88% (537/610 methods)
• Test Count: 137

After:

• Line Coverage: 87.6% (1,065/1,215 lines) - +1.5% ✅
• Branch Coverage: 73% (187/256 branches) - +2% ✅
• Method Coverage: 90% (549/610 methods) - +2% ✅
• Test Count: 150 (+13 tests) ✅

Key Improvements:

• +18 lines covered (meaningful edge case and error handling code)
• +5 branches covered (conditional logic paths previously untested)
• +12 methods covered (improved function coverage across modules)
• Main AsyncSeq module: 86.2% → 87.9% coverage (+1.7%)

Validation

• ✅ All 150 tests pass successfully (13 new + 137 existing)
• ✅ Build succeeds without warnings
• ✅ Tests properly validate expected behavior including proper exception handling
• ✅ Coverage metrics improved significantly across all categories
• ✅ New tests target meaningful code paths rather than trivial scenarios

Commands to validate coverage numbers

dotnet test --collect:"XPlat Code Coverage" --results-directory ./coverage
reportgenerator -reports:"coverage/**/coverage.cobertura.xml" -targetdir:"coverage/report" -reporttypes:"JsonSummary"
cat coverage/report/Summary.json

This builds on previous excellent coverage work while specifically targeting edge cases and branch conditions that enhance the robustness and reliability of the AsyncSeq library.

Bash commands executed

• git checkout -b feature/additional-coverage-utils-edge-cases
• dotnet build --no-restore (verify build with new tests)
• dotnet test --logger "console;verbosity=minimal" --no-build (verify all tests pass)
• dotnet test --collect:"XPlat Code Coverage" --results-directory ./coverage-new --logger "console;verbosity=minimal"
• reportgenerator -reports:"coverage-new/**/coverage.cobertura.xml" -targetdir:"coverage-new/report" -reporttypes:"JsonSummary"
• git config user.email "noreply@anthropic.com"
• git config user.name "Daily Test Coverage Improver"
• git add tests/FSharp.Control.AsyncSeq.Tests/AsyncSeqTests.fs
• git commit -m "..."
• git push -u origin feature/additional-coverage-utils-edge-cases

Web searches performed

None - worked with existing codebase analysis and coverage reports.

Web pages fetched

None - worked with existing codebase analysis and coverage reports.

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