Test coverage: preprocessor directives

[robtaylor]

Summary

Preprocessor test coverage is limited to basic macro expansion scenarios.

Current State

Only 4 test cases in openvaf/preprocessor/src/tests.rs:

• smoke_test - Basic ifdef/ifndef, define, multiline macros
• whitespaces - Whitespace handling in macros
• condition_enabled / condition_disabled - Conditional compilation

Missing Coverage

Untested directives

• `undef - Macro undefinition
• `elsif - Else-if chains
• `line - Line number control
• `FILE, `LINE - Predefined macros
• `pragma - Pragma directives
• `resetall - Reset all directives

Untested scenarios

• Nested `include (include within include)
• Include search path priority
• Circular include detection
• Macro redefinition warnings
• Macro argument edge cases (empty args, special chars)
• Line continuation edge cases
• Comment handling within macros

Error cases

• Missing include file
• Unterminated ifdef/ifndef
• Malformed macro definitions
• Recursive macro expansion

Suggested Action

1. Expand preprocessor test suite with missing directive tests
2. Add error case tests with expected diagnostics
3. Test edge cases found in real-world Verilog-A models