[IMPROVEMENT] Add test case for cascade-failure behavior in nicediff

[Hell1213]

[IMPROVEMENT]

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Adds test case to document cascade-failure behavior in nicediff comparison algorithm.

Fixes #1087

What This Does

When comparing subtitle files where one file is missing an entry, the current line-by-line comparison causes all subsequent lines to mismatch. This test documents that behavior for future reference when implementing the frame-offset-tolerant comparison algorithm planned for the GSoC Sample Platform NG project.

Changes

Added test_cascade_failure_missing_entry() to tests/test_test/test_diff.py that creates a scenario where subtitle entry 2 is missing and verifies the cascade behavior occurs.

Testing

python -m unittest tests.test_test.test_diff -v

All tests pass.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud