Closes #9

README.md

@@ -21,8 +21,8 @@ The implementation follows a simple and practical design:
 - the same decode engine can be reused for live traffic and trace replay
 
 The core library uses C++17 and has no Qt dependency. Qt Core and Qt Test are
-required only for the regression tests. Live CAN acquisition, trace-file readers,
-and a Qt model adapter are left to the consuming application.
+used by the regression tests; the optional adapter requires Qt Core. Live CAN acquisition, trace-file readers,
+are left to the consuming application. An optional Qt Core model adapter is provided in `qt/`.
 
 See [changelog.md](changelog.md) for the release and development history,
 [tests/README.md](tests/README.md) for test instructions, and
@@ -55,7 +55,7 @@ DbcTreeBuilder
    ↓
 TreeNode hierarchy
    ↓
-future Qt UI
+DbcTreeModel → Qt views
 ```
 
 ### 2. Runtime decode path
@@ -114,7 +114,8 @@ This avoids forcing UI-oriented structures into a decode role they were not mean
 ```text
 core/       C++17 parser, statement handlers, metadata, tree, and decoder
 examples/   Command-line demo (built separately)
-tests/      QtTest parser and decoder regression suites
+qt/         Optional read-only Qt Core model adapter
+tests/      Parser, decoder, tree, and optional model tests
 docs/       Generated Doxygen documentation
 dbc.pro     Root qmake project: core + tests
 Doxyfile    API documentation configuration
@@ -235,7 +236,7 @@ has no metadata payload. The payload types are:
 - `FrameInfo`
 - `SignalInfo`
 
-The tree is intended for browsing and later Qt model integration.
+The tree supports browsing through the optional `DbcTreeModel` adapter.
 
 It is **not** the primary runtime decode structure.
 
@@ -884,7 +885,7 @@ nonnegative `uint64_t`; when constructing mappings manually, normalize keys
 with `NormalizeValueKey()` before insertion.
 
 Named `VAL_TABLE_` tables, environment-variable mappings, multiline statements,
-and Qt presentation are outside this implementation.
+are outside this implementation; the optional Qt adapter exposes signal mappings.
 
 ---
 
@@ -942,9 +943,6 @@ A practical development order would be:
 
 Recommended additions:
 
-- parent pointer in `TreeNode`
-- Qt model adapter
-- better display strings for UI
 - selective decoding of only chosen signals
 
 ### Stage 3
@@ -1009,6 +1007,99 @@ make -j
 
 qmake is still the build tool; this target does not link Qt libraries.
 
+### Optional Qt model adapter
+
+Requires Qt 5.11 or newer (including Qt 6) for `QAbstractItemModelTester`.
+The adapter itself links only Qt Core. Enable its library and focused QtTest suite:
+
+```sh
+mkdir -p build-qt
+cd build-qt
+qmake6 ../dbc.pro CONFIG+=dbc_qt
+make -j
+make check
+```
+
+Consumers include `qt/qt.pri` instead of `core/core.pri`, and set
+`DBC_CORE_BUILD_DIR` and `DBC_QT_BUILD_DIR` to the corresponding library build
+directories when building separately. A widget application also needs `QT += widgets`. The adapter integration enables
+`no_keywords`, because core metadata has a `signals` member; use `Q_SIGNALS`,
+`Q_SLOTS`, and `Q_EMIT` in consuming Qt classes.
+
+```cpp
+#include "dbc_parser.h"
+#include "dbc_tree_builder.h"
+#include "dbc_tree_model.h"
+#include <QTreeView>
+
+// Run after constructing QApplication; view owns the model through QObject.
+QTreeView view;
+auto *model = new DbcTreeModel(&view);
+model->SetTree(DbcTreeBuilder().Build(DbcParser().ParseFile("example.dbc")));
+view.setModel(model);
+view.expandAll();
+view.show();
+// On reload, pass a newly built tree to SetTree(); to clear:
+// model->SetTree(nullptr);
+```
+
+The root is invisible: frames are top-level rows, signals are their children.
+Only column zero has children. `parent()` always returns column zero.
+The model takes exclusive ownership of the tree; do not retain mutable aliases.
+Metadata is copied by the tree builder, so the parsed database may be destroyed.
+`TreeNode::GetParent()` is non-owning and `GetRow()` gives the zero-based sibling
+position (zero for a detached node/root). Nodes cannot be copied or moved;
+transferring their `unique_ptr` ownership preserves addresses and navigation.
+
+Call `SetTree()` on the model's thread. It accepts a detached Root or nullptr,
+uses `beginResetModel()`/`endResetModel()`, and destroys the previous tree during
+reset. All ordinary QModelIndex values expire on reset and must not be reused;
+QPersistentModelIndex values are invalidated by Qt. Destroying the model also
+invalidates indexes. Invalid and foreign indexes return no data/flags/children.
+Valid items are enabled and selectable, with no editing support.
+
+| Column (zero-based enum) | Frame display | Signal display |
+| --- | --- | --- |
+| 0 `Name` | Name | Name |
+| 1 `CanId` | Normalized hexadecimal ID | Empty |
+| 2 `PayloadLength` | Bytes | Empty |
+| 3 `StartBit` | Empty | DBC start bit |
+| 4 `BitLength` | Empty | Bit count |
+| 5 `ByteOrder` | Empty | Intel / Motorola |
+| 6 `Signed` | Empty | Signed / Unsigned |
+| 7 `Unit` | Empty | Unit |
+| 8 `Comment` | Comment | Comment |
+
+Horizontal DisplayRole headers describe these columns; other header requests
+return invalid QVariant. ToolTipRole returns the comment on every column.
+Custom roles also apply on every column; inapplicable roles return invalid QVariant:
+
+| Role | Node types | QVariant content |
+| --- | --- | --- |
+| `NodeTypeRole` | Frame, signal | int corresponding to NodeType |
+| `CanIdRole`, `PayloadLengthRole`, `ExtendedRole` | Frame | uint, int, bool |
+| `StartBitRole`, `BitLengthRole` | Signal | uint |
+| `LittleEndianRole`, `SignedRole` | Signal | bool |
+| `UnitRole` | Signal | QString |
+| `CommentRole` | Frame, signal | QString |
+| `ValueDescriptionsRole` | Signal | QVariantList of QVariantMap entries |
+
+Each value-description entry contains `value` (qlonglong for negative keys,
+qulonglong for nonnegative keys) and `description` (QString). This preserves the
+full signed/unsigned 64-bit range without converting through double. An unmapped
+signal returns an empty list. Data comes from `SignalInfo::valueDescriptions`.
+Unsupported roles return invalid QVariant.
+
+### Standalone tree tests without Qt
+
+From the repository root, use only a C++17 compiler:
+
+```sh
+c++ -std=c++17 -Icore tests/tree_node_test.cpp core/tree_node.cpp \
+  core/dbc_tree_builder.cpp -o /tmp/dbc_tree_node_test
+/tmp/dbc_tree_node_test
+```
+
 ### Build and run the demo
 
 After building core, run these commands from the repository root:

changelog.md

@@ -10,6 +10,14 @@ existing Git tag; subsequent changes are listed as unreleased.
 
 #### Added
 
+- Added non-owning TreeNode parent navigation and stable sibling positions;
+  disabled node moves to preserve links while retaining unique_ptr ownership.
+- Added optional read-only Qt Core DbcTreeModel with documented columns and
+  metadata roles, exact VAL_ entries, exclusive tree ownership, and reset-based
+  reload/clear support. Core remains independent of Qt.
+- Added QAbstractItemModelTester coverage, navigation/metadata/reset tests,
+  a standalone Qt-free tree test, and adapter build and usage documentation.
+
 - Added `VAL_` signal value descriptions through the statement dispatcher and
   factory, with complete syntax validation, exact signed/unsigned 64-bit keys,
   deferred reference resolution, duplicate detection, and source error locations.

core/tree_node.cpp

@@ -24,8 +24,11 @@ TreeNode::TreeNode(const SignalInfo &signal)
 }
 
 void TreeNode::AddChild(std::unique_ptr<TreeNode> child) {
-    if (child)
+    if (child) {
         m_children.push_back(std::move(child));
+        m_children.back()->m_parent = this;
+        m_children.back()->m_row = m_children.size() - 1U;
+    }
 }
 
 std::size_t TreeNode::GetChildCount() const {
@@ -61,3 +64,11 @@ const FrameInfo *TreeNode::GetFrame() const {
 const SignalInfo *TreeNode::GetSignal() const {
     return m_signal.get();
 }
+
+const TreeNode *TreeNode::GetParent() const {
+    return m_parent;
+}
+
+std::size_t TreeNode::GetRow() const {
+    return m_row;
+}

core/tree_node.h

@@ -56,8 +56,8 @@ public:
     TreeNode(const TreeNode &) = delete;
     TreeNode &operator=(const TreeNode &) = delete;
 
-    TreeNode(TreeNode &&) = default;
-    TreeNode &operator=(TreeNode &&) = default;
+    TreeNode(TreeNode &&) = delete;
+    TreeNode &operator=(TreeNode &&) = delete;
 
     /**
      * @brief Add child node.
@@ -65,6 +65,12 @@ public:
      */
     void AddChild(std::unique_ptr<TreeNode> child);
 
+    /** Non-owning parent; nullptr for a detached node or the root. */
+    const TreeNode *GetParent() const;
+
+    /** Zero-based sibling position; zero for a detached node or the root. */
+    std::size_t GetRow() const;
+
     /**
      * @brief Get child count.
      * @return Number of children.
@@ -110,6 +116,8 @@ public:
     const SignalInfo *GetSignal() const;
 
 private:
+    TreeNode *m_parent = nullptr;
+    std::size_t m_row = 0U;
     NodeType m_type;
     std::string m_name;
     std::vector<std::unique_ptr<TreeNode>> m_children;

dbc.pro

@@ -3,3 +3,10 @@ SUBDIRS += core tests
 core.subdir = core
 tests.subdir = tests
 tests.depends = core
+contains(CONFIG, dbc_qt) {
+    SUBDIRS += qt model_tests
+    qt.subdir = qt
+    qt.depends = core
+    model_tests.file = tests/model_tests.pro
+    model_tests.depends = qt
+}

qt/dbc_tree_model.cpp

@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: MIT
+#include "dbc_tree_model.h"
+#include <QVariantList>
+#include <QVariantMap>
+#include <limits>
+#include <stdexcept>
+
+DbcTreeModel::DbcTreeModel(QObject *parent) : QAbstractItemModel(parent) {}
+
+void DbcTreeModel::SetTree(std::unique_ptr<TreeNode> root) {
+    if (root && (root->GetType() != NodeType::Root || root->GetParent()))
+        throw std::invalid_argument("Model requires a detached root node");
+    beginResetModel();
+    m_root = std::move(root);
+    endResetModel();
+}
+
+const TreeNode *DbcTreeModel::Node(const QModelIndex &index) const {
+    if (!index.isValid() || index.model() != this || index.column() < 0 ||
+        index.column() >= ColumnCount || index.row() < 0)
+        return nullptr;
+    return static_cast<const TreeNode *>(index.internalPointer());
+}
+
+QModelIndex DbcTreeModel::index(int row, int column, const QModelIndex &parentIndex) const {
+    if (row < 0 || column < 0 || column >= ColumnCount ||
+        (parentIndex.isValid() && parentIndex.column() != 0))
+        return {};
+    const TreeNode *owner = parentIndex.isValid() ? Node(parentIndex) : m_root.get();
+    if (!owner)
+        return {};
+    const TreeNode *child = owner->GetChild(static_cast<std::size_t>(row));
+    return child ? createIndex(row, column, const_cast<TreeNode *>(child)) : QModelIndex();
+}
+
+QModelIndex DbcTreeModel::parent(const QModelIndex &childIndex) const {
+    const TreeNode *child = Node(childIndex);
+    const TreeNode *owner = child ? child->GetParent() : nullptr;
+    if (!owner || owner == m_root.get())
+        return {};
+    return createIndex(static_cast<int>(owner->GetRow()), 0, const_cast<TreeNode *>(owner));
+}
+
+int DbcTreeModel::rowCount(const QModelIndex &parentIndex) const {
+    if (parentIndex.isValid() && parentIndex.column() != 0)
+        return 0;
+    const TreeNode *owner = parentIndex.isValid() ? Node(parentIndex) : m_root.get();
+    if (!owner)
+        return 0;
+    return static_cast<int>(qMin(owner->GetChildCount(), static_cast<std::size_t>(std::numeric_limits<int>::max())));
+}
+
+int DbcTreeModel::columnCount(const QModelIndex &parentIndex) const {
+    return parentIndex.isValid() && !Node(parentIndex) ? 0 : ColumnCount;
+}
+
+QVariant DbcTreeModel::data(const QModelIndex &item, int role) const {
+    const TreeNode *node = Node(item);
+    if (!node)
+        return {};
+    const FrameInfo *frame = node->GetFrame();
+    const SignalInfo *signal = node->GetSignal();
+    const QString comment = QString::fromStdString(frame ? frame->comment : signal ? signal->comment
+                                                                                   : "");
+    if (role == Qt::ToolTipRole || role == CommentRole)
+        return comment;
+    if (role == NodeTypeRole)
+        return static_cast<int>(node->GetType());
+    if (role == ValueDescriptionsRole && signal) {
+        QVariantList descriptions;
+        for (const auto &entry: signal->valueDescriptions) {
+            QVariantMap pair;
+            if (const auto *number = std::get_if<std::int64_t>(&entry.first))
+                pair.insert("value", QVariant::fromValue(static_cast<qlonglong>(*number)));
+            else
+                pair.insert("value", QVariant::fromValue(static_cast<qulonglong>(std::get<std::uint64_t>(entry.first))));
+            pair.insert("description", QString::fromStdString(entry.second));
+            descriptions.append(pair);
+        }
+        return descriptions;
+    }
+    if (frame) {
+        if (role == CanIdRole) return frame->canId;
+        if (role == PayloadLengthRole) return static_cast<int>(frame->dlc);
+        if (role == ExtendedRole) return frame->isExtended;
+    }
+    if (signal) {
+        if (role == StartBitRole) return signal->startBit;
+        if (role == BitLengthRole) return signal->length;
+        if (role == LittleEndianRole) return signal->isLittleEndian;
+        if (role == SignedRole) return signal->isSigned;
+        if (role == UnitRole) return QString::fromStdString(signal->unit);
+    }
+    if (role != Qt::DisplayRole) return {};
+    switch (item.column()) {
+        case Name:
+            return QString::fromStdString(node->GetName());
+        case CanId:
+            return frame ? QVariant(QString("0x%1").arg(frame->canId, 0, 16).toUpper()) : QVariant();
+        case PayloadLength:
+            return frame ? QVariant(static_cast<int>(frame->dlc)) : QVariant();
+        case StartBit:
+            return signal ? QVariant(signal->startBit) : QVariant();
+        case BitLength:
+            return signal ? QVariant(signal->length) : QVariant();
+        case ByteOrder:
+            return signal ? QVariant(signal->isLittleEndian ? "Intel" : "Motorola") : QVariant();
+        case Signed:
+            return signal ? QVariant(signal->isSigned ? "Signed" : "Unsigned") : QVariant();
+        case Unit:
+            return signal ? QVariant(QString::fromStdString(signal->unit)) : QVariant();
+        case Comment:
+            return comment;
+        default:
+            return {};
+    }
+}
+
+QVariant DbcTreeModel::headerData(int section, Qt::Orientation orientation, int role) const {
+    static const char *const headers[] = {"Name", "CAN ID", "Payload (bytes)", "Start bit", "Length (bits)", "Byte order", "Signedness", "Unit", "Comment"};
+    if (orientation != Qt::Horizontal || role != Qt::DisplayRole || section < 0 || section >= ColumnCount)
+        return {};
+    return QString::fromLatin1(headers[section]);
+}
+
+Qt::ItemFlags DbcTreeModel::flags(const QModelIndex &item) const {
+    return Node(item) ? Qt::ItemIsEnabled | Qt::ItemIsSelectable : Qt::NoItemFlags;
+}

qt/dbc_tree_model.h

@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: MIT
+#ifndef DBC_TREE_MODEL_H
+#define DBC_TREE_MODEL_H
+
+#include "tree_node.h"
+#include <QAbstractItemModel>
+
+/** Read-only model. Owns an immutable tree; all indexes expire on SetTree().
+ * Use QPersistentModelIndex to observe reset invalidation. Call on the model thread.
+ */
+class DbcTreeModel : public QAbstractItemModel {
+public:
+    enum Column { Name,
+                  CanId,
+                  PayloadLength,
+                  StartBit,
+                  BitLength,
+                  ByteOrder,
+                  Signed,
+                  Unit,
+                  Comment,
+                  ColumnCount };
+    // Metadata roles apply on every column; inapplicable roles return invalid QVariant.
+    enum Role { NodeTypeRole = Qt::UserRole + 1,
+                CanIdRole,
+                PayloadLengthRole,
+                StartBitRole,
+                BitLengthRole,
+                LittleEndianRole,
+                SignedRole,
+                UnitRole,
+                CommentRole,
+                ValueDescriptionsRole,
+                ExtendedRole };
+
+    explicit DbcTreeModel(QObject *parent = nullptr);
+    void SetTree(std::unique_ptr<TreeNode> root);
+    QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const override;
+    QModelIndex parent(const QModelIndex &child) const override;
+    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
+    int columnCount(const QModelIndex &parent = QModelIndex()) const override;
+    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;
+    QVariant headerData(int section, Qt::Orientation orientation, int role = Qt::DisplayRole) const override;
+    Qt::ItemFlags flags(const QModelIndex &index) const override;
+
+private:
+    const TreeNode *Node(const QModelIndex &index) const;
+    std::unique_ptr<TreeNode> m_root;
+};
+#endif

qt/qt.pri

@@ -0,0 +1,11 @@
+include($$PWD/../core/core.pri)
+QT += core
+INCLUDEPATH += $$PWD
+isEmpty(DBC_QT_BUILD_DIR): DBC_QT_BUILD_DIR = $$clean_path($$OUT_PWD/../qt)
+# Put the adapter before core for static linker dependency ordering.
+LIBS = -L$$DBC_QT_BUILD_DIR -ldbc_qt $$LIBS
+win32-msvc*: DBC_QT_LIBRARY = $$DBC_QT_BUILD_DIR/dbc_qt.lib
+else: DBC_QT_LIBRARY = $$DBC_QT_BUILD_DIR/libdbc_qt.a
+PRE_TARGETDEPS += $$DBC_QT_LIBRARY
+
+CONFIG += no_keywords

qt/qt.pro

@@ -0,0 +1,11 @@
+TEMPLATE = lib
+TARGET = dbc_qt
+CONFIG += staticlib c++17
+QT += core
+QT -= gui
+include(../core/core.pri)
+HEADERS += dbc_tree_model.h
+SOURCES += dbc_tree_model.cpp
+CONFIG -= debug_and_release debug_and_release_target
+
+CONFIG += no_keywords

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.

tests/dbc_tree_model_test.cpp

@@ -0,0 +1,136 @@
+#include "dbc_parser.h"
+#include "dbc_tree_builder.h"
+#include "dbc_tree_model.h"
+#include <QAbstractItemModelTester>
+#include <QSignalSpy>
+#include <QTemporaryFile>
+#include <QtTest>
+#include <limits>
+
+static std::unique_ptr<TreeNode> ParsedTree() {
+    QTemporaryFile fixture;
+    if (!fixture.open()) throw std::runtime_error("Fixture creation failed");
+    fixture.write("BO_ 256 Status: 8 ECU\n SG_ State : 0|8@1+ (1,0) [0|255] \"rpm\" ECU\n"
+                  " SG_ Other : 8|8@1+ (1,0) [0|255] \"\" ECU\n"
+                  "BO_ 257 Second: 8 ECU\n SG_ Value : 0|8@1+ (1,0) [0|255] \"\" ECU\n"
+                  "CM_ BO_ 256 \"Frame comment\";\nCM_ SG_ 256 State \"Signal comment\";\n"
+                  "VAL_ 256 State -1 \"Negative\" 0 \"Off\" 18446744073709551615 \"Maximum\";\n");
+    fixture.flush();
+    return DbcTreeBuilder().Build(DbcParser().ParseFile(fixture.fileName().toStdString()));
+}
+
+class ModelTest : public QObject {
+    Q_OBJECT
+private Q_SLOTS:
+    void navigation() {
+        DbcTreeModel model;
+        QAbstractItemModelTester tester(&model, QAbstractItemModelTester::FailureReportingMode::QtTest);
+        QCOMPARE(model.rowCount(), 0);
+        model.SetTree(ParsedTree());
+        QCOMPARE(model.rowCount(), 2);
+        for (int row = 0; row < model.rowCount(); ++row) {
+            const QModelIndex frame = model.index(row, 0);
+            for (int column = 0; column < model.columnCount(); ++column) {
+                const QModelIndex frameColumn = model.index(row, column);
+                QVERIFY(!model.parent(frameColumn).isValid());
+                QCOMPARE(model.rowCount(frameColumn), column == 0 ? (row == 0 ? 2 : 1) : 0);
+                for (int signalRow = 0; signalRow < model.rowCount(frame); ++signalRow) {
+                    const QModelIndex signal = model.index(signalRow, column, frame);
+                    QCOMPARE(model.parent(signal), frame);
+                    QCOMPARE(model.rowCount(signal), 0);
+                    QVERIFY(!model.index(0, 0, signal).isValid());
+                    QCOMPARE(model.flags(signal), Qt::ItemIsEnabled | Qt::ItemIsSelectable);
+                }
+            }
+        }
+        QVERIFY(!model.index(-1, 0).isValid());
+        QVERIFY(!model.index(2, 0).isValid());
+        QVERIFY(!model.index(0, -1).isValid());
+        QVERIFY(!model.index(0, model.columnCount()).isValid());
+        QVERIFY(!model.index(0, 0, model.index(0, 1)).isValid());
+        QVERIFY(!model.parent({}).isValid());
+        QVERIFY(!model.data({}).isValid());
+        QCOMPARE(model.flags({}), Qt::NoItemFlags);
+        DbcTreeModel other;
+        other.SetTree(ParsedTree());
+        const QModelIndex foreign = other.index(0, 0);
+        QVERIFY(!model.index(0, 0, foreign).isValid());
+        QVERIFY(!model.parent(foreign).isValid());
+        QCOMPARE(model.rowCount(foreign), 0);
+        QCOMPARE(model.columnCount(foreign), 0);
+        QVERIFY(!model.data(foreign).isValid());
+        QCOMPARE(model.flags(foreign), Qt::NoItemFlags);
+    }
+    void metadata() {
+        DbcTreeModel model;
+        model.SetTree(ParsedTree());
+        const QModelIndex frame = model.index(0, 0);
+        const QModelIndex signal = model.index(0, 0, frame);
+        QCOMPARE(model.data(frame).toString(), QString("Status"));
+        QCOMPARE(model.data(model.index(0, DbcTreeModel::CanId)).toString(), QString("0X100"));
+        QCOMPARE(model.data(frame, DbcTreeModel::CanIdRole).toUInt(), 256U);
+        QCOMPARE(model.data(frame, DbcTreeModel::PayloadLengthRole).toInt(), 8);
+        QCOMPARE(model.data(signal, DbcTreeModel::UnitRole).toString(), QString("rpm"));
+        const QVariantList expectedSignal = {"State", QVariant(), QVariant(), 0U, 8U,
+                                             "Intel", "Unsigned", "rpm", "Signal comment"};
+        const QVariantList expectedFrame = {"Status", "0X100", 8, QVariant(), QVariant(),
+                                            QVariant(), QVariant(), QVariant(), "Frame comment"};
+        for (int column = 0; column < model.columnCount(); ++column) {
+            QCOMPARE(model.data(model.index(0, column, frame)), expectedSignal.at(column));
+            QCOMPARE(model.data(model.index(0, column)), expectedFrame.at(column));
+        }
+        QCOMPARE(model.data(frame, DbcTreeModel::NodeTypeRole).toInt(), static_cast<int>(NodeType::Frame));
+        QCOMPARE(model.data(signal, DbcTreeModel::NodeTypeRole).toInt(), static_cast<int>(NodeType::Signal));
+        QCOMPARE(model.data(frame, DbcTreeModel::ExtendedRole).toBool(), false);
+        QVERIFY(!model.data(frame, DbcTreeModel::ValueDescriptionsRole).isValid());
+        QVERIFY(model.data(model.index(1, 0, frame), DbcTreeModel::ValueDescriptionsRole).toList().isEmpty());
+
+        QCOMPARE(model.data(signal, Qt::ToolTipRole).toString(), QString("Signal comment"));
+        QCOMPARE(model.data(signal, DbcTreeModel::StartBitRole).toUInt(), 0U);
+        QCOMPARE(model.data(signal, DbcTreeModel::BitLengthRole).toUInt(), 8U);
+        QCOMPARE(model.data(signal, DbcTreeModel::LittleEndianRole).toBool(), true);
+        QCOMPARE(model.data(signal, DbcTreeModel::SignedRole).toBool(), false);
+        QVERIFY(!model.data(signal, DbcTreeModel::CanIdRole).isValid());
+        QVERIFY(!model.data(frame, DbcTreeModel::UnitRole).isValid());
+        QVERIFY(!model.data(frame, Qt::EditRole).isValid());
+        const QVariantList values = model.data(signal, DbcTreeModel::ValueDescriptionsRole).toList();
+        QCOMPARE(values.size(), 3);
+        QCOMPARE(values.at(0).toMap().value("value").toLongLong(), -1LL);
+        QCOMPARE(values.at(2).toMap().value("value").toULongLong(), std::numeric_limits<qulonglong>::max());
+        QCOMPARE(values.at(2).toMap().value("description").toString(), QString("Maximum"));
+        for (int column = 0; column < model.columnCount(); ++column) {
+            QVERIFY(model.headerData(column, Qt::Horizontal).isValid());
+            QCOMPARE(model.data(model.index(0, column, frame), DbcTreeModel::ValueDescriptionsRole), QVariant(values));
+        }
+        QVERIFY(!model.headerData(-1, Qt::Horizontal).isValid());
+        QVERIFY(!model.headerData(model.columnCount(), Qt::Horizontal).isValid());
+        QVERIFY(!model.headerData(0, Qt::Vertical).isValid());
+    }
+    void replacement() {
+        DbcTreeModel model;
+        QAbstractItemModelTester tester(&model, QAbstractItemModelTester::FailureReportingMode::QtTest);
+        QSignalSpy resets(&model, &QAbstractItemModel::modelReset);
+        model.SetTree(ParsedTree());
+        QPersistentModelIndex frame(model.index(0, 0));
+        QPersistentModelIndex signal(model.index(0, 4, frame));
+        model.SetTree(ParsedTree());
+        QVERIFY(!frame.isValid());
+        QVERIFY(!signal.isValid());
+        QCOMPARE(model.rowCount(), 2);
+        QPersistentModelIndex replacement(model.index(1, 0));
+        model.SetTree(nullptr);
+        QVERIFY(!replacement.isValid());
+        QCOMPARE(model.rowCount(), 0);
+        QVERIFY(!model.index(0, 0).isValid());
+        model.SetTree(nullptr);
+        QCOMPARE(resets.count(), 4);
+        try {
+            model.SetTree(std::unique_ptr<TreeNode>(new TreeNode(FrameInfo())));
+            QFAIL("A frame cannot be the invisible model root");
+        } catch (const std::invalid_argument &) {
+        }
+        QCOMPARE(resets.count(), 4);
+    }
+};
+QTEST_GUILESS_MAIN(ModelTest)
+#include "dbc_tree_model_test.moc"

tests/model_tests.pro

@@ -0,0 +1,8 @@
+TEMPLATE = app
+TARGET = dbc_model_tests
+QT += core testlib
+QT -= gui
+CONFIG += console testcase c++17 no_keywords
+CONFIG -= app_bundle debug_and_release debug_and_release_target
+include(../qt/qt.pri)
+SOURCES += dbc_tree_model_test.cpp

tests/tree_node_test.cpp

@@ -0,0 +1,33 @@
+// Standalone C++17 test: no Qt required.
+#include "dbc_tree_builder.h"
+#include <stdexcept>
+#include <type_traits>
+
+static void Check(bool condition) {
+    if (!condition) throw std::runtime_error("Tree navigation test failed");
+}
+
+int main() {
+    static_assert(!std::is_move_constructible<TreeNode>::value, "Node addresses must be stable");
+    DbcDatabase database;
+    FrameInfo frame;
+    SignalInfo signal;
+    frame.signals.push_back(signal);
+    frame.signals.push_back(signal);
+    database.frames.push_back(frame);
+    database.frames.push_back(frame);
+    auto root = DbcTreeBuilder().Build(database);
+    Check(root->GetParent() == nullptr && root->GetRow() == 0);
+    root->AddChild(nullptr);
+    Check(root->GetChildCount() == 2 && !root->GetChild(2));
+    for (std::size_t row = 0; row < root->GetChildCount(); ++row) {
+        const TreeNode *child = root->GetChild(row);
+        Check(child->GetParent() == root.get() && child->GetRow() == row);
+        for (std::size_t position = 0; position < child->GetChildCount(); ++position) {
+            const TreeNode *leaf = child->GetChild(position);
+            Check(leaf->GetParent() == child && leaf->GetRow() == position);
+        }
+    }
+    auto transferred = std::move(root);
+    Check(transferred->GetChild(0)->GetParent() == transferred.get());
+}