Added comprehensive tests to capture parent-child relationship bugs:
- Test 1: Detect Earth becoming child of spacecraft (exact FIXME bug)
- Test 2: Validate mass hierarchy (massive bodies never have small parents)
- Test 3: Detect invalid config placeholder values (bodies at same position)
- Test 4: Mutual SOI edge case (similar-mass planets within SOI)
All tests fail as expected, documenting bugs for future fixes.
Tests 1-3 will pass after spacecraft separation fix.
Test 4 captures separate mutual SOI issue.
Files:
- docs/test_plan_invalid_parent_assignment.md (test plan)
- tests/test_invalid_parent_assignment.cpp (4 test cases)
- tests/configs/mutual_soi_close.toml (edge case config)
