Add pgTAP testing infrastructure

[tobyhede]

Summary

This PR introduces pgTAP as a robust testing framework for EQL, providing industry-standard PostgreSQL testing capabilities alongside the existing custom assertion helpers.

What's Included

Task 1: Install and Configure pgTAP ✅

• Docker Integration: Created Dockerfile.pgtap that extends official PostgreSQL images (14-17) and installs pgTAP 1.3.5
• Docker Compose: Updated docker-compose.yml to build custom images with pgTAP for all PostgreSQL versions
• Installation Script: Added tests/install_pgtap.sql to install and verify the pgTAP extension
• Test Runner: Created tasks/test-pgtap.sh - a mise task to run pgTAP tests with PostgreSQL version selection

Task 2: Structure Testing Suite ✅

Created comprehensive structure tests in tests/pgtap/structure/:

• schema_test.sql (10 tests): Verifies eql_v2 schema, eql_v2_encrypted type, and eql_v2_configuration table structure
• types_test.sql (7 tests): Verifies all index term types exist (blake3, hmac_256, bloom_filter, ORE variants)
• functions_test.sql (9 tests): Verifies key functions exist with correct signatures (comparison, config management)
• operators_test.sql (1 test): Verifies operators exist for eql_v2_encrypted type

All structure tests passing ✓

Task 3: Functionality Testing Suite (Partial) ✅

• equality_test.sql (13 tests): Converted existing equality operator tests to pgTAP format
  • Tests eql_v2_encrypted = eql_v2_encrypted with HMAC and Blake3 indexes
  • Tests eql_v2.eq() function
  • Tests eql_v2_encrypted = jsonb and jsonb = eql_v2_encrypted operations
  • Includes both positive (matching) and negative (no match) test cases

Testing

All tests pass successfully:

mise run test  # Existing tests still pass

pgTAP tests can be run with:

mise run test-pgtap

Benefits

• Industry Standard: pgTAP follows the TAP (Test Anything Protocol) standard used across the PostgreSQL ecosystem
• Rich Assertions: Provides specialized assertions for schema testing, function signatures, and more
• Better Organization: Clear separation between structure tests and functionality tests
• CI Integration: TAP output format enables easy integration with CI/CD pipelines
• Maintainability: Well-documented testing framework makes it easier for contributors

Implementation Plan

This PR implements Tasks 1-3 from docs/pgtap-implementation-plan.md. Remaining tasks:

• Task 3.2-3.5: Additional functionality tests (comparison, JSONB operators, config, index terms)
• Task 4: Data seeding patterns documentation
• Task 5: CI pipeline integration
• Task 6: Testing documentation and migration guides
• Task 7: Advanced testing enhancements

Related

Based on the implementation plan in docs/pgtap-implementation-plan.md