Fix bug in group manager initialisation and add test

com.zsmartsystems.zigbee/src/main/java/com/zsmartsystems/zigbee/groups/ZigBeeNetworkGroupManager.java

@@ -113,7 +113,16 @@ public ZigBeeNetworkGroupManager(ZigBeeNetworkManager networkManager) {
     }
 
     public void initialize() {
-        networkManager.readNetworkDataStore(DATASTORE_KEY_GROUPS);
+        Set<ZigBeeGroupDao> daoSet = (Set<ZigBeeGroupDao>) networkManager.readNetworkDataStore(DATASTORE_KEY_GROUPS);
+        if (daoSet == null) {
+            return;
+        }
+
+        for (ZigBeeGroupDao dao : daoSet) {
+            ZigBeeGroup group = new ZigBeeGroup(networkManager, 0);
+            group.setDao(dao);
+            networkGroups.put(group.getGroupId(), group);
+        }
     }
 
     public void shutdown() {

com.zsmartsystems.zigbee/src/test/java/com/zsmartsystems/zigbee/groups/ZigBeeNetworkGroupManagerTest.java

@@ -0,0 +1,48 @@
+/**
+ * Copyright (c) 2016-2024 by the respective copyright holders.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ */
+package com.zsmartsystems.zigbee.groups;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.junit.Test;
+import org.mockito.Mockito;
+
+import com.zsmartsystems.zigbee.ZigBeeNetworkManager;
+
+/**
+ * Tests for {@link ZigBeeNetworkGroupManager}
+ *
+ * @author Chris Jackson
+ *
+ */
+public class ZigBeeNetworkGroupManagerTest {
+
+    @Test
+    public void initialize() {
+        ZigBeeNetworkManager networkManager = Mockito.mock(ZigBeeNetworkManager.class);
+        ZigBeeNetworkGroupManager groupManager = new ZigBeeNetworkGroupManager(networkManager);
+
+        assertTrue(groupManager.getAll().isEmpty());
+        groupManager.initialize();
+        assertTrue(groupManager.getAll().isEmpty());
+
+        Set<ZigBeeGroupDao> daoSet = new HashSet<>();
+        daoSet.add(new ZigBeeGroupDao());
+
+        Mockito.when(networkManager.readNetworkDataStore(any())).thenReturn(daoSet);
+
+        assertTrue(groupManager.getAll().isEmpty());
+        groupManager.initialize();
+        assertEquals(1, groupManager.getAll().size());
+    }
+}