Daily Test Coverage Improver: Add CSV functionality tests

[github-actions]

Summary

• Significantly improved CSV module test coverage from 30.3% to 62.8% (+32.5%)
• Added 32 comprehensive tests in new CsvFile.fs test module
• Achieved specific coverage improvements: CsvFile (0% → 85.5%), CsvRow (0% → 100%), StringExtensions (0% → 77.1%)

Test Coverage Details

This pull request addresses the CSV functionality which previously had 0% coverage for core classes. The new tests cover:

CsvFile Class Tests

• Parse methods with various options (headers, separators, quotes, skipRows, ignoreErrors)
• Load methods from streams and TextReader
• Column index retrieval (GetColumnIndex, TryGetColumnIndex)
• Error handling for invalid operations

CsvRow Class Tests

• Column access by index and name (GetColumn, indexers)
• Dynamic operator functionality (row?ColumnName)
• Complete coverage of all access methods

StringExtensions Tests

• Type conversion methods: AsInteger, AsInteger64, AsDecimal, AsFloat, AsBoolean, AsDateTime, AsGuid
• Proper error handling for invalid input values
• Edge cases and format variations

Test Quality

• All 32 tests are passing
• Comprehensive edge case coverage including custom separators, quoted values, multiline content
• Proper exception testing using NUnit Assert.Throws pattern
• Follows F# coding conventions and project structure

Coverage Impact

• Overall project coverage: 34.3% → 35.9% (+1.6%)
• CSV module specific: 30.3% → 62.8% (+32.5% improvement)
• Individual class improvements: CsvFile 0%→85.5%, CsvRow 0%→100%, StringExtensions 0%→77.1%

This automated improvement was generated by the Daily Test Coverage Improver workflow to systematically address low-coverage areas in the codebase.

🤖 Generated with Claude Code