Daily Test Coverage Improver: Comprehensive CSV Core coverage improvements

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Summary

Significantly improved CSV Core test coverage with 30 new comprehensive tests addressing the 30% coverage area identified in previous analysis.

• Added comprehensive CsvFile.Parse functionality tests
• Added CsvFile column indexing and error handling tests
• Added CsvExtensions validation for invalid input scenarios
• Added extensive CSV parsing edge case coverage
• All 2305+ existing tests continue to pass

Problems Found

Coverage analysis revealed major gaps in CSV Core functionality:

• CsvFile.Parse options (separators, quotes, headers, skipRows, ignoreErrors) were inadequately tested
• Column indexing methods (GetColumnIndex, TryGetColumnIndex) lacked comprehensive validation
• CsvExtensions error scenarios for invalid conversions were untested
• CSV parsing edge cases (empty fields, line endings, special characters) needed coverage
• Error handling and boundary conditions were under-tested

Actions Taken

Added 30 new CSV Core tests covering:

1. CsvFile.Parse functionality:

   • Custom separators (;, |, tab)
   • Custom quote characters (' instead of ")
   • Headers vs. no headers parsing
   • Row skipping capability
   • Error handling with ignoreErrors flag
   • Malformed row detection

2. CsvFile column operations:

   • GetColumnIndex for valid and invalid columns
   • TryGetColumnIndex returning Some/None appropriately
   • Proper exception throwing for missing columns
   • Column access by name and index

3. CsvExtensions error scenarios:

   • AsInteger, AsInteger64, AsDecimal, AsFloat with invalid strings
   • AsBoolean, AsDateTime, AsGuid with malformed input
   • Culture-specific parsing validation
   • Proper exception handling for all conversion failures

4. CSV parsing edge cases:

   • Empty fields handling (a,,c)
   • Trailing commas (a,b,)
   • Quoted empty strings (a,"",c)
   • Mixed quoted/unquoted fields
   • Various line endings (Windows \r\n, Unix \n, Mac \r)
   • Different separators (comma, semicolon, tab, pipe)
   • BOM (Byte Order Mark) handling
   • Single field CSV files
   • Internal quotes in quoted fields

Coverage Improvements Achieved

Before: CSV Core identified as 30% coverage area (lowest priority after WorldBank and JSON work)
After: Comprehensive test suite covering major CSV functionality gaps

Test Count: Added 30 new tests (from ~17 CSV tests to ~47 CSV tests)

Note: Precise coverage percentages require running the full coverage analysis pipeline, which can be verified with:

dotnet test tests/FSharp.Data.Core.Tests/FSharp.Data.Core.Tests.fsproj --collect:"Code Coverage" --results-directory ./TestResults/
reportgenerator -reports:"TestResults/**/*.coverage" -targetdir:"TestResults/CoverageReport" -reporttypes:"Html;TextSummary"

Test Performance

Addresses maintainer feedback about CI performance:

• All tests are fast unit tests with no external dependencies
• Focus on in-memory CSV processing only
• No file I/O, network calls, or slow operations
• Tests execute in milliseconds

Future Areas for Improvement

Based on analysis, next opportunities include:

• FSharp.Data.Runtime.Utilities: 50.8% coverage (text conversion utilities)
• FSharp.Data.Http: 74.6% coverage (HTTP client functionality)
• FSharp.Data.Html.Core: Various HTML parsing modules
• CSV inference logic for type detection
• CSV schema validation functionality

Validation

• ✅ All 30 new tests pass successfully
• ✅ All 2305+ existing tests continue to pass
• ✅ Build succeeds without warnings or errors
• ✅ Code formatting applied (Fantomas validation passes)
• ✅ No regression in other components

Commands Executed

Bash commands:

• git checkout -b daily-test-improver/csv-core-coverage
• dotnet build tests/FSharp.Data.Core.Tests/FSharp.Data.Core.Tests.fsproj --configuration Debug
• dotnet test tests/FSharp.Data.Core.Tests/FSharp.Data.Core.Tests.fsproj --filter "Name~Csv"
• dotnet test tests/FSharp.Data.Core.Tests/FSharp.Data.Core.Tests.fsproj --no-build
• dotnet run --project build/build.fsproj -- -t Format
• git add ... && git commit ... && git push ...

MCP Functions:

• mcp__github__search_issues - Located research issue Daily Test Coverage Improver: Research and Plan #1533
• mcp__github__get_issue_comments - Read maintainer feedback and previous work status
• mcp__github__search_pull_requests - Reviewed previous coverage improvements (WorldBank, JSON)
• File operations: Read, Edit for test implementation

Web Searches: None performed
Web Pages Fetched: None

AI-generated content by Daily Test Coverage Improver may contain mistakes.