Issue/123 improve test coverage

[hoijnet]

This PR improves test coverage for terminusdb_client/woqlquery/woql_query.py, increasing coverage from 85% to 94% (+9 percentage points).

Before (main branch):

• Overall coverage*: 85% (7303/8598 lines)
• Total tests: 591

• All the test files were also part of coverage measurement

After:

• Overall coverage*: 95% (13294/14036 lines)
• Total tests: 1356 (+765 tests)

• Test files no longer part of coverage measurement

Test Files Created (19 new files, 765 new tests)

Core Test Files

1. test_woql_core.py - Core WOQL query functionality tests
2. test_woql_query_overall.py - Overall query integration tests
3. test_woql_query_edge_cases.py - General query edge cases
4. test_woql_test_helpers.py - Test helper utilities and fixtures

Edge Case & Advanced Tests

5. test_woql_edge_cases_extended.py - Vocabulary, select, as(), cursor, arithmetic, Doc/Vars
6. test_woql_advanced_features.py - Advanced filtering, aggregation, subqueries, recursive queries, complex patterns
7. test_woql_remaining_edge_cases.py - Args introspection for 30+ methods, distinct, as() edge cases

Operation-Specific Tests

8. test_woql_set_operations.py - Concat, join, sum, slice, set operations (member, difference, intersection, union)
9. test_woql_graph_operations.py - Graph modification, queries, traversal, analytics, context, updates, metadata
10. test_woql_path_operations.py - Path operations, triple/quad operations, added/removed triples
11. test_woql_json_operations.py - JSON serialization, document handling, type conversions
12. test_woql_subquery_aggregation.py - Subquery execution, aggregation functions, group by, having clauses

Builder & Utility Tests

13. test_woql_query_builder.py - Query builder methods, internal functions, contains_update checks
14. test_woql_cursor_management.py - Cursor positioning, movement, state management, data value cleaning
15. test_woql_utility_methods.py - Find last subject, same entry comparison, string matching, triple builder context
16. test_woql_utility_functions.py - Set operations, list operations, arithmetic, comparison, string, regex, document operations

Type System & Validation Tests

17. test_woql_type_system.py - Type conversion, inference, custom types, validation, data types, coercion
18. test_woql_type.py - Type handling and type-related operations
19. test_woql_schema_validation.py - Schema validation, type checking, vocabulary loading, cursor wrapping, select/distinct validation

Bug Fixes

1. woql_query.py line 355 - Fixed _data_value_list bug (incorrect method call: clean_data_value → _clean_data_value)
2. woql_query.py lines 852-857 - Added defensive programming for And array initialization to prevent edge case failures
3. test_woql_path_operations.py line 9 - Fixed pytest.skip syntax error
4. test_woql_query_builder.py lines 195-212 - Updated deprecated test implementation

Discovery on select() Design Change

The select() predicate should likely take no arguments too as a valid case across both python and javascript client. The documentation is now updated.

Comparison with JavaScript Client

When unsure, verified against the JavaScript client (terminusdb-client-js) to ensure consistency:

• Args introspection feature matches JS client behavior (also disabled in JS for quad operations, "args" would not be possible as a value with the args discovery and introspection/reflection is a better way to achieve the goal)
• Method signatures and return values align with JS equivalents
• Error handling patterns consistent across both clients

Documentation Created

• docs/KNOWN_ISSUES_AND_UNCOVERED_CODE.md - Comprehensive catalog of remaining issues, bugs, and uncovered code organized by severity and category

Next Steps

To improve coverage and quality:

1. Address known issues documented in docs/KNOWN_ISSUES_AND_UNCOVERED_CODE.md
2. Add tests for schema/builder operations
3. Consider removing deprecated _data_value_list() method after deprecation period
4. Consider deprecating and removing the "args" first argument introspection feature