[IMPROVEMENT]: Add ATSC XMLTV regression test coverage via Alembic migration

[x15sr71]

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Summary

Add regression test coverage for ATSC XMLTV output generation (--xmltv=1) using the ATSC broadcast sample I uploaded to the platform.

This test exercises:

• ATSC PSI/SI table parsing (VCT, ETT, EIT)
• XMLTV format generation from broadcast EPG data
• Exit code validation (expected_rc=10) with OutputType.null

Technical Details

Sample Selection

Sample 187 (ch29FullTS.ts) – ATSC broadcast sample for XMLTV testing with --xmltv=1 --out=null:

• SHA256: 6b10f8aef895469ec9cb89ecd0c2463eb2442052c32da9d81c6a6f5cec9137b8
• Size: 300.52 MB | Duration: 2m 10s
• ATSC PSI/SI Tables:
  • Virtual Channel Table (VCT) - channels 5.1-5.5 (KPIX-TV, StartTV, etc.)
  • Extended Text Table (ETT) - program titles/descriptions
  • Event Information Table (EIT) - multi-day EPG scheduling
• Captions: EIA-608/708 across 5 video PIDs

I reviewed the TS samples currently available on the platform and did not find any that contain the ATSC PSI/SI tables (VCT, EIT, ETT) needed to exercise the ATSC XMLTV generation paths. For this reason, I recently added an ATSC broadcast sample to provide regression coverage.

Database Deployment Strategy

Following the pattern from the WebVTT PR (#993):

Environment	Sample Used	Mechanism	Purpose
Production	Sample 187	Alembic migration	Real ATSC XMLTV validation
Fresh install	Samples 1-2	install/sample_db.py	Bootstrap without FK errors
CI Tests	Samples 1-2	tests/base.py fixtures	Fast smoke tests

Why no test fixture changes:

• Sample 187 is a 300MB production upload (not in test fixtures)
• Adding it would cause foreign key violations in test DB
• Migration-only registration follows the existing pattern for uploaded samples

Test Characteristics

• OutputType.null: Exit-code-only validation (no golden file comparison)
• expected_rc = 10: Correct ATSC XMLTV processing return code
• ignore = false: Standard validation (no special error handling)
• Category: "General" - Uses existing category for organization
• Idempotent: Migration checks for existing test before inserting (safe to re-run)

Migration Details

• Revision: eb7303e132c0
• Revises: c8f3a2b1d4e5 (latest migration on master)
• Creates: Regression test + category linkage + output metadata
• Downgrade: Clean removal in correct FK order

Related Work

• [FIX]: Restore XMLTV generation for ATSC EIT/VCT streams and correct EIT bounds checks ccextractor#1773 — ATSC XMLTV implementation
• [FIX]: Add ATSC VCT virtual channel numbers and call signs to XMLTV output ccextractor#1837 — ATSC table parsing

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
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

[cfsmp3]

• Migration-head collision: revises head c8f3a2b1d4e5 — but so does #1071. Second to merge → two alembic heads → flask db upgrade breaks.
• Contradictory output row: correct='', ignore=0 will perpetually diff, yet the PR claims "exit-code-only" validation. Pick one (set ignore=1, or store a real hash).

[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

[x15sr71]

Thanks for the review and suggesting the fix — fixed the output-row contradiction and found a MySQL-only blocker, fixed it too:

• Output row (fixed): set ignore=1 → exit-code-only, matching the PR's intent. Checked against CCExtractorTester: with ignore=1 it reports an exit-code-only result and never compares output, so there's no perpetual diff.
• ignore reserved word (new — blocker): the raw INSERT listed ignore unquoted, which passes on SQLite (CI) but fails with ERROR 1064 on MySQL/prod. Backticked it.

Head collision: If #1071 merges first, I'm happy to rebase this PR onto it. Just let me know your preferred order.