pdftract/notes/bf-18a0w.md

Verification Note for bf-18a0w: Improve Assertion Messages and Verify Test Correctness

Summary

Improved assertion messages across all tests in cmap_unmapped_glyphs.rs to provide maximally helpful failure diagnostics. All 7 tests pass successfully.

Changes Made

File Modified

• crates/pdftract-core/tests/cmap_unmapped_glyphs.rs

Assertion Message Improvements

Test 1: test_cmap_unmapped_glyph_skip

Enhanced assertion messages for:

• is_unmapped_glyph_name() checks - Added detailed failure messages explaining expected vs found and why this matters
• map.is_empty() check - Explains why empty map indicates parser error
• map.len() check - Details expected count and why incorrect count matters
• map.lookup() checks - Added expected/found/why matters for each lookup
• Unicode destination validation loop - Enhanced message about replacement character detection

Test 2: test_cmap_multiple_mappings_with_unmapped_check

Enhanced assertion messages for:

• map.len() check - Added context about beginbfchar...endbfchar parsing
• Individual mapping lookups (0x00, 0x01, 0x02) - Added expected/found/why matters for each
• is_unmapped_glyph_name() check - Explains function should not be affected by parsing

Test 3: test_cmap_range_mapping_with_unmapped_awareness

Enhanced assertion messages for:

• Range expansion check - Explains beginbfrange...endbfrange behavior and why 26 mappings expected
• First/last entry checks - Added context about Unicode code points (U+0041 for A, U+005A for Z)
• Unmapped glyph name checks - Clarified leading slash handling

Tests 4-7: Already had excellent assertion messages

These tests already had detailed, helpful assertion messages from previous work:

• test_differences_overlay_filters_unmapped_glyphs
• test_differences_overlay_consecutive_with_unmapped_filtering
• test_differences_overlay_filters_null_glyph
• test_differences_overlay_filters_all_g_series_unmapped

Assertion Message Pattern

All assertion messages now follow this pattern for maximum helpfulness:

1. What was expected - Clear statement of the expected result
2. What was found - The actual result (using {:?} formatting for complex values)
3. Why this matters - Context about the assertion's purpose and implications

Example:

assert_eq!(
    map.len(),
    3,
    "CMAP should have exactly 3 mappings. \
     Expected: 3 mappings (A, B, C). \
     Found: {} mappings. \
     Why this matters: Incorrect mapping count indicates the parser is incorrectly \
     handling the beginbfchar...endbfchar construct.",
    map.len()
);

Test Results

All 7 tests pass successfully:

running 7 tests
test test_cmap_multiple_mappings_with_unmapped_check ... ok
test test_cmap_range_mapping_with_unmapped_awareness ... ok
test test_cmap_unmapped_glyph_skip ... ok
test test_differences_overlay_consecutive_with_unmapped_filtering ... ok
test test_differences_overlay_filters_null_glyph ... ok
test test_differences_overlay_filters_all_g_series_unmapped ... ok
test test_differences_overlay_filters_unmapped_glyphs ... ok

test result: ok. 7 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

Verification of Skip Behavior

The tests correctly verify the skip behavior through:

1. Positive assertions - Normal glyphs (A, B, C, space, CustomA, CustomB, Z) ARE present in CMAP output
2. Negative assertions - Unmapped glyphs (g001-g003, g000-g009, .notdef, .null) are ABSENT from CMAP output
3. Configuration awareness - Tests reference build/unmapped-glyph-names.json to explain why glyphs should be filtered

Edge Cases and Limitations

Edge Cases Covered

• Consecutive name assignments in /Differences arrays
• Leading slash on glyph names (/.notdef vs .notdef)
• Range mapping (beginbfrange...endbfrange)
• Multiple individual mappings (beginbfchar...endbfchar)
• Complete filtering (all entries are unmapped)

Known Limitations

• Tests use hardcoded CMAP data structures rather than real PDF files
• Tests do not cover every possible CMAP format variation (focus on common cases)
• Tests assume build/unmapped-glyph-names.json contains the expected unmapped glyph names

Acceptance Criteria Status

✅ All assertion messages are clear and specific

• Every assertion now follows the expected/found/why matters pattern
• Messages provide context about configuration (e.g., referencing build/unmapped-glyph-names.json)

✅ Test runs without panics or errors

• All 7 tests complete successfully with no errors

✅ Test correctly identifies skip behavior

• Positive assertions verify normal glyphs are preserved
• Negative assertions verify unmapped glyphs are filtered
• Tests use the actual is_unmapped_glyph_name() and DifferencesOverlay::parse() functions

✅ Test provides helpful diagnostics on failure

• Assertion messages explain what went wrong, what was expected, and why it matters
• Complex values are formatted using {:?} for easy debugging

Commit Information

Commit: bf-18a0w - Improve assertion messages and verify test correctness

Files Changed:

• crates/pdftract-core/tests/cmap_unmapped_glyphs.rs

Test Verification: All 7 tests in cmap_unmapped_glyphs pass (0.00s)