Add comprehensive unit test suite with 237 tests across 13 test classes

This commit introduces extensive test coverage for the railway interlocking simulator:

**Test Coverage:**
- Utility tests (204 tests): Doubleton, EnumUnorientedGraph, HashMapGraph, TreeMultiMap
- Context tests (10 tests): DefaultContext operations, concurrent XML serialization
- Simulation tests (16 tests): Train behavior, InOutWorker, ShuntingLoop scenarios
- XML tests (7 tests): XMLContextFactory parsing and validation with 10 fixture files

**Test Infrastructure:**
- MockSimulationContext: Mock implementation for isolated testing
- TestContextBuilder: Fluent API for building test contexts
- TestFixtures: Shared test data and configurations
- TestTrackBuilder: Simplified track layout construction

**Build Enhancements:**
- Mockito 5.7.0 integration for mocking framework
- Test resources directory support in build.xml
- JUnit assertions enabled (-ea flag)
- XML test result reporting

**Source Code Fixes:**
- DefaultContext.moveCell: Implement cell movement logic
- XMLContextFactory.saveContext: Fix isolated node serialization
- Train/InOutWorker: Add null pointer validation
- Doubleton/TreeMultiMap: Add deprecation notices

**Documentation Updates:**
- CLAUDE.md: Update test coverage documentation (237 tests, 13 classes)
- Package structure: Add testutil and test fixtures sections
- Test utilities: Document builders and mock implementations

All tests pass with `ant test`. This establishes a strong foundation for maintaining code quality while preserving the legacy 2007 codebase.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: bedaHovorka

CLAUDE.md

@@ -284,13 +284,28 @@ src/
 │   └── resources/cz/vutbr/fit/interlockSim/
 │       └── resource/              - XML schemas and configuration files
 └── test/
-    └── java/cz/vutbr/fit/interlockSim/
-        ├── util/
-        │   └── Array2DMapTest.java    - Array2DMap unit tests (JUnit 5)
-        ├── objects/cells/
-        │   └── CellTest.java          - Cell unit tests (JUnit 5)
-        └── context/
-            └── ContextTest.java       - Context unit tests (JUnit 5)
+    ├── java/cz/vutbr/fit/interlockSim/
+    │   ├── context/               - Context and serialization tests
+    │   │   ├── ConcurrentSaveTest.java
+    │   │   └── DefaultContextTest.java
+    │   ├── sim/                   - Simulation scenario tests
+    │   │   ├── InOutWorkerTest.java
+    │   │   ├── ShuntingLoopTest.java
+    │   │   └── TrainTest.java
+    │   ├── testutil/              - Test utilities and builders
+    │   │   ├── MockSimulationContext.java
+    │   │   ├── TestContextBuilder.java
+    │   │   ├── TestFixtures.java
+    │   │   └── TestTrackBuilder.java
+    │   ├── util/                  - Utility class tests
+    │   │   ├── DoubletonTest.java
+    │   │   ├── EnumUnorientedGraphTest.java
+    │   │   ├── HashMapGraphTest.java
+    │   │   └── TreeMultiMapTest.java
+    │   └── xml/                   - XML parsing and validation tests
+    │       └── XMLContextFactoryTest.java
+    └── resources/cz/vutbr/fit/interlockSim/xml/
+        └── fixtures/              - Test XML files (10 fixtures)
 
 jdisco/                            - Third-party discrete event simulation library (Java 6, separate Maven module)
 ```
@@ -317,17 +332,42 @@ This is a working historical codebase from 2007. Stability and preservation are
 
 ## Testing
 
-JUnit 5.10.1 tests with AssertJ assertions located in `src/test/java/cz/vutbr/fit/interlockSim/`. All dependencies are managed via Apache Ivy.
+Comprehensive JUnit 5.10.1 test suite with AssertJ assertions located in `src/test/java/cz/vutbr/fit/interlockSim/`. All dependencies are managed via Apache Ivy.
 
 **Test framework:**
 - JUnit 5 (Jupiter API and Engine)
 - JUnit Platform for Ant integration
 - AssertJ 3.24.2 for fluent assertions
 
-**Current tests:**
+**Test coverage (237 tests across 13 test classes):**
+
+**Utility tests:**
 - `Array2DMapTest` - 10 tests for 2D array-based map implementation
-- `CellTest` - 2 tests for cell segment and direction logic
-- `ContextTest` - 4 tests for railway network context operations
+- `DoubletonTest` - 66 tests for immutable ordered pair data structure
+- `EnumUnorientedGraphTest` - 55 tests for enum-based unoriented graph
+- `HashMapGraphTest` - 48 tests for HashMap-based graph implementation
+- `TreeMultiMapTest` - 25 tests for tree-based multimap implementation
+
+**Context tests:**
+- `DefaultContextTest` - 8 tests for railway network context operations
+- `ConcurrentSaveTest` - 2 tests for thread-safe XML serialization
+
+**Simulation tests:**
+- `TrainTest` - 6 tests for train behavior and state management
+- `InOutWorkerTest` - 8 tests for entry/exit point worker operations
+- `ShuntingLoopTest` - 2 tests for shunting loop simulation scenario
+
+**XML tests:**
+- `XMLContextFactoryTest` - 7 tests for XML parsing and validation with 10 fixture files
+
+**Test utilities:**
+- `MockSimulationContext` - Mock implementation for testing
+- `TestContextBuilder` - Fluent builder for test contexts
+- `TestFixtures` - Shared test data and configurations
+- `TestTrackBuilder` - Fluent builder for test track layouts
+
+**Test resources:**
+- `src/test/resources/cz/vutbr/fit/interlockSim/xml/fixtures/` - 10 XML test fixtures for parser validation
 
 **Run tests:**
 ```bash

build.xml

@@ -31,6 +31,7 @@ Ivy integration: 2025
     <property name="src.main.java" location="src/main/java"/>
     <property name="src.test.java" location="src/test/java"/>
     <property name="src.main.resources" location="src/main/resources"/>
+    <property name="src.test.resources" location="src/test/resources"/>
 
     <!-- Build directories -->
     <property name="build.main" location="build/main"/>
@@ -171,21 +172,32 @@ Or use Docker:
                debug="true">
             <classpath refid="test.classpath"/>
         </javac>
+
+        <!-- Copy test resources to build directory -->
+        <copy todir="${build.test}">
+            <fileset dir="${src.test.resources}"/>
+        </copy>
     </target>
 
     <target name="test" depends="compile-test" description="Run tests">
         <echo message="Running tests..."/>
+        <mkdir dir="${build.test}/test-results"/>
         <junitlauncher printsummary="yes"
                        haltonfailure="yes">
             <classpath>
                 <path refid="test.classpath"/>
                 <pathelement location="${build.test}"/>
             </classpath>
 
-            <testclasses outputdir="${build.test}">
+            <testclasses outputdir="${build.test}/test-results">
                 <fileset dir="${build.test}">
                     <include name="**/*Test.class"/>
                 </fileset>
+                <!-- Enable Java assertions for tests (requires fork) -->
+                <fork>
+                    <jvmarg value="-ea"/>
+                </fork>
+                <listener type="legacy-xml" sendSysOut="true" sendSysErr="true"/>
                 <listener type="legacy-plain" sendSysOut="true"/>
             </testclasses>
         </junitlauncher>

ivy.xml

@@ -40,6 +40,10 @@
         <!-- AssertJ: Fluent assertions library -->
         <dependency org="org.assertj" name="assertj-core" rev="3.24.2" conf="test->default"/>
 
+        <!-- Mockito: Mocking framework for testing -->
+        <dependency org="org.mockito" name="mockito-core" rev="5.7.0" conf="test->default"/>
+        <dependency org="org.mockito" name="mockito-junit-jupiter" rev="5.7.0" conf="test->default"/>
+
         <!-- SLF4J API 1.7.x: Logging facade (matches jDisco dependency) -->
         <dependency org="org.slf4j" name="slf4j-api" rev="1.7.36" conf="compile->default"/>
 

src/main/java/cz/vutbr/fit/interlockSim/context/DefaultContext.java

@@ -381,17 +381,14 @@ public void removeLine(TrackBlock line) {
 	}
 
 	public void moveCell(Point from, Point to) {
-		// EXTENSION
-//		final Cell fromCell = getGrid().get(from);
-//		if (!(fromCell instanceof NodeCell)) return;
-//		final Cell toCell = getGrid().get(to);
-//		if (toCell != null) {
-//			setChanged();
-//			notifyObservers("Move: Target occupied");
-//			return;
-//		}
-//		final NodeCell nodeCell = (NodeCell) fromCell;
-//		//zkusit najit
+		final Cell fromCell = getGrid().get(from);
+		if (!(fromCell instanceof NodeCell)) return;
+
+		final Cell toCell = getGrid().get(to);
+		if (toCell != null) return;
+
+		putCell(to, (NodeCell)fromCell);
+		removeCell(from);
 	}
 
 	public Segment getSegment(final PathSeparator separator, final Track track, final Track secondEndTrack) {

src/main/java/cz/vutbr/fit/interlockSim/sim/InOutWorker.java

@@ -40,6 +40,12 @@ public class InOutWorker extends LoopProcess {
 	 * @param out
 	 */
 	public InOutWorker(SimulationContext context, InOut out) {
+		if (context == null) {
+			throw new NullPointerException("context must not be null");
+		}
+		if (out == null) {
+			throw new NullPointerException("out must not be null");
+		}
 		this.inOut = out;
 		this.context = context;
 		this.next = context.getNextTrackSection(inOut, null);

src/main/java/cz/vutbr/fit/interlockSim/sim/Train.java

@@ -495,6 +495,12 @@ protected void derivatives() {
 	 * @param timetable
 	 */
 	public Train(SimulationContext context, Timetable timetable) {
+		if (context == null) {
+			throw new NullPointerException("context must not be null");
+		}
+		if (timetable == null) {
+			throw new NullPointerException("timetable must not be null");
+		}
 		this.context = context;
 		this.timetable = timetable;
 		this.length = timetable.getLength();

src/main/java/cz/vutbr/fit/interlockSim/util/Doubleton.java

@@ -18,6 +18,8 @@
  * Represents combination of two elements
  * @param <T> type of elements
  * @param <V> type of additional information
+ *
+ * @deprecated should be replaced in kotlin with library thing like Pair
  */
 public class Doubleton<T,V> extends AbstractSet<T> {
 	enum IteratorState {

src/main/java/cz/vutbr/fit/interlockSim/util/TreeMultiMap.java

@@ -22,6 +22,8 @@
  *
  * @param <K> key
  * @param <V> value
+ *
+ * @deprecated should be replaced by some standard library implementation in Kotlin
  */
 public class TreeMultiMap<K,V> {
 	private final SortedMap<K,Set<V>> map = new TreeMap<K,Set<V>>();

src/main/java/cz/vutbr/fit/interlockSim/xml/XMLContextFactory.java

@@ -339,11 +339,28 @@ public boolean saveContext(Context context, File file) {
 			stringBuilder.append(">\n");
 			fileWriter.write(stringBuilder.toString());
 
-			for (Point p : xmlContext.getGraph().nodeSet()) {
+			// Save all NodeCells from the grid (including isolated nodes)
+			// Use LinkedHashSet to avoid duplicates while preserving insertion order
+			final java.util.Set<Point> allNodes = new java.util.LinkedHashSet<Point>();
+
+			// Add all nodes from the graph (nodes with connections)
+			allNodes.addAll(xmlContext.getGraph().nodeSet());
+
+			// Add any isolated NodeCells from the grid that aren't in the graph
+			for (java.util.Map.Entry<Point, Cell> entry : railWayNetGrid) {
+				if (entry.getValue() instanceof cz.vutbr.fit.interlockSim.objects.cells.NodeCell) {
+					allNodes.add(entry.getKey());
+				}
+			}
+
+			// Write all nodes to XML
+			for (Point p : allNodes) {
 				final Cell cell = railWayNetGrid.get(p);
-				StringBuilder builder = tagFor(p, cell);
-				spacing(builder, 1);
-				fileWriter.write(builder.toString());
+				if (cell instanceof cz.vutbr.fit.interlockSim.objects.cells.NodeCell) {
+					StringBuilder builder = tagFor(p, cell);
+					spacing(builder, 1);
+					fileWriter.write(builder.toString());
+				}
 			}
 
 			for (Map.Entry<Doubleton<Point, Segment>, TrackBlock> i : xmlContext.getGraph().entrySet()) {
@@ -360,10 +377,11 @@ public boolean saveContext(Context context, File file) {
 
 			fileWriter.write("</" + ROOT_ELEMENT_NAME + ">\n");
 			fileWriter.close();
+			return true;
 		} catch (IOException e) {
 			assert false : e;
+			return false;
 		}
-		return false;
 	}
 
 	//jednotici metoda...