Daily Test Coverage Improver: Add comprehensive async transformation and state management tests

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Summary

Added 11 comprehensive tests focusing on async transformations, state management, and edge cases. This continues the excellent coverage improvement work while targeting functions with meaningful async behavior patterns.

Problems Found

• Async transformation patterns: Limited testing of mapAsync ordering guarantees and exception propagation
• State management functions: scanAsync and threadStateAsync lacked comprehensive validation
• Filtering operations: chooseAsync and filterAsync needed edge case testing
• Utility functions: lastOrDefault and fold edge cases were undertested
• Performance scenarios: Large sequence handling in ofSeq needed validation

Actions Taken

Async Transformation Tests (4 tests):

• AsyncSeq.mapAsync should preserve order with async transformations - Tests ordering guarantees with variable async delays
• AsyncSeq.mapAsync should propagate exceptions - Tests exception handling in async transformations
• AsyncSeq.chooseAsync should filter and transform - Tests async choose with Option-based filtering
• AsyncSeq.filterAsync should work with async predicates - Tests async predicate evaluation

State Management Tests (3 tests):

• AsyncSeq.scan should work with accumulator - Tests synchronous accumulator function
• AsyncSeq.scanAsync should work with async accumulator - Tests async accumulator with state
• AsyncSeq.threadStateAsync should maintain state correctly - Tests stateful transformation patterns

Edge Case Tests (3 tests):

• AsyncSeq.fold with empty sequence should return seed - Tests fold behavior with empty input
• AsyncSeq.lastOrDefault should return default for empty sequence - Tests default value handling
• AsyncSeq.lastOrDefault should return last element - Tests correct last element extraction

Performance Test (1 test):

• AsyncSeq.ofSeq should work with large sequence - Tests conversion of 1000-element sequence

Changes in Test Coverage Achieved

Before:

• Line Coverage: 86.8% (1052/1211 lines)
• Branch Coverage: 73.2% (186/254 branches)
• Method Coverage: 89.2% (542/607 methods)
• Test Count: 144

After:

• Line Coverage: 87.3% (1058/1211 lines) - +0.5% ✅
• Branch Coverage: 74.8% (190/254 branches) - +1.6% ✅
• Method Coverage: 89.7% (545/607 methods) - +0.5% ✅
• Test Count: 155 (+11 tests) ✅

Net Result: +6 lines, +4 branches, +3 methods covered with meaningful tests targeting async patterns and edge cases that enhance library robustness.

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 the excellent foundation established by previous PRs (182-188) while focusing on async transformation patterns that are commonly used but were undertested.

Bash commands executed

• git checkout -b feature/test-coverage-delay-tryWith-finalizers
• dotnet build --no-restore
• dotnet test --no-build --logger "console;verbosity=minimal"
• 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/test-coverage-delay-tryWith-finalizers

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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