Add comprehensive checklist for tracking test fixes

Co-authored-by: renemadsen <76994+renemadsen@users.noreply.github.com>

Author: Copilot

failing_tests_checklist.md

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+# Failing Tests Checklist - MariaDB 11.6.2
+
+This document provides a categorized checklist of failing test classes for tracking fixes.
+
+## Priority 1: RETURNING Clause Issues (Critical)
+
+- [ ] TwoDatabasesMySqlTest (4 tests)
+  - [ ] Can_set_connection_string_in_interceptor (2 variants)
+  - [ ] Can_query_from_one_connection_string_and_save_changes_to_another
+  - [ ] Can_query_from_one_connection_and_save_changes_to_another
+
+- [ ] CompositeKeyEndToEndMySqlTest (3 tests)
+  - [ ] Can_use_generated_values_in_composite_key_end_to_end
+  - [ ] Only_one_part_of_a_composite_key_needs_to_vary_for_uniqueness
+  - [ ] Can_use_two_non_generated_integers_as_composite_key_end_to_end
+
+- [ ] MySqlMigrationsSqlGeneratorTest (9 tests)
+  - [ ] UpdateDataOperation_all_args_composite_multi
+  - [ ] UpdateDataOperation_required_args_multiple_rows
+  - [ ] UpdateDataOperation_all_args_multi
+  - [ ] UpdateDataOperation_all_args
+  - [ ] UpdateDataOperation_required_args_multi
+  - [ ] UpdateDataOperation_required_args
+  - [ ] UpdateDataOperation_all_args_composite
+  - [ ] (additional update operations)
+
+## Priority 2: Type Mapping Issues (High)
+
+- [ ] NorthwindStringIncludeQueryMySqlTest (2 tests)
+  - [ ] Multi_level_includes_are_applied_with_skip_take (async/sync)
+
+- [ ] NorthwindChangeTrackingQueryMySqlTest (2 tests)
+  - [ ] Entity_range_does_not_revert_when_attached_dbContext
+  - [ ] Entity_range_does_not_revert_when_attached_dbSet
+
+- [ ] NorthwindMiscellaneousQueryMySqlTest (multiple tests)
+  - [ ] OrderBy_skip_take_take
+  - [ ] (additional LEAST-related tests)
+
+## Priority 3: Graph Updates (High - likely cascade from Priority 1)
+
+- [ ] GraphUpdatesMySqlClientCascadeTest (985 tests)
+- [ ] GraphUpdatesMySqlClientNoActionTest (820 tests)
+- [ ] ProxyGraphUpdatesMySqlTest+LazyLoading (303 tests)
+- [ ] ProxyGraphUpdatesMySqlTest+ChangeTrackingAndLazyLoading (303 tests)
+- [ ] ProxyGraphUpdatesMySqlTest+ChangeTracking (303 tests)
+
+**Note:** These tests likely fail due to RETURNING clause issues. Re-test after Priority 1 is fixed.
+
+## Priority 4: Query Translation (High)
+
+- [ ] Query.* test classes (6,681 tests across various query test suites)
+  - [ ] NorthwindQueryFiltersQueryMySqlTest
+  - [ ] NorthwindStringIncludeQueryMySqlTest
+  - [ ] NorthwindChangeTrackingQueryMySqlTest
+  - [ ] NorthwindMiscellaneousQueryMySqlTest
+  - [ ] (many other Northwind query test classes)
+
+**Note:** Review after Priority 1 and 2 fixes to identify remaining issues.
+
+## Priority 5: Other Test Classes (Medium)
+
+- [ ] BulkUpdates.* (94 tests)
+- [ ] StoreGeneratedMySqlTest (87 tests)
+- [ ] ManyToManyTrackingMySqlTest (68 tests)
+- [ ] KeysWithConvertersMySqlTest (47 tests)
+- [ ] MigrationsMySqlTest (21 tests)
+- [ ] UpdatesMySqlTest (20 tests)
+- [ ] Update.* (20 tests)
+- [ ] OptimisticConcurrencyMySqlTest (18 tests)
+- [ ] SaveChangesInterceptionMySqlTestBase variants (32 tests)
+- [ ] FieldMappingMySqlTest (12 tests)
+- [ ] Scaffolding.* (9 tests)
+- [ ] TableSplittingMySqlTest (7 tests)
+
+## Testing Strategy
+
+1. **Fix Priority 1** (RETURNING clause support)
+   - Implement MariaDB detection
+   - Replace RETURNING with ROW_COUNT()/LAST_INSERT_ID()
+   - Re-run full test suite
+
+2. **Fix Priority 2** (LEAST function type mapping)
+   - Add type mapping for LEAST function
+   - Test affected query tests
+
+3. **Re-evaluate Priority 3 & 4**
+   - Many tests may pass after Priority 1 & 2 fixes
+   - Identify remaining failures
+
+4. **Address remaining issues**
+   - Update test baselines for MariaDB-specific SQL
+   - Fix any remaining query translation issues
+
+---
+
+## Progress Tracking
+
+- [ ] Priority 1 fixes implemented
+- [ ] Priority 2 fixes implemented
+- [ ] Full test suite re-run after P1+P2
+- [ ] Priority 3 re-evaluated
+- [ ] Priority 4 re-evaluated
+- [ ] All fixes verified
+- [ ] Documentation updated
+
+---
+
+**Total Tests:** 30,173
+**Currently Failing:** 9,874 (32.7%)
+**Target:** < 1% failure rate after all fixes