Closes #9

tests/README.md

@@ -59,3 +59,16 @@ automatically.
 
 Dispatch tests also verify exact keyword matching, handler construction and reuse,
 unknown statements, and independent parsing sessions, including recovery after errors.
+
+## Tree and optional model tests
+
+`tree_node_test.cpp` is a standalone C++17 executable without Qt; see the root
+README for its compiler command. It checks parents, sibling positions, null
+children, bounds, and unique_ptr transfer.
+
+Enable `CONFIG+=dbc_qt` in the root qmake invocation to build `dbc_qt` and
+`dbc_model_tests` alongside existing tests. Qt 5.11+ or Qt 6 is required.
+`make check` runs all suites. Model tests parse a temporary DBC fixture and use
+QAbstractItemModelTester, verify navigation across columns, invalid/foreign
+indexes, metadata and exact VAL_ integers, and persistent-index invalidation
+when reloading or clearing the tree. No GUI/display server is needed.