BAEL-1983 Intialize a HashMap in Java (#4819)

core-java-collections/src/test/java/com/baeldung/java/map/initialize/MapInitializerUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.java.map.initialize;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.Map;
+
+import org.junit.Test;
+
+public class MapInitializerUnitTest {
+    
+    @Test
+    public void givenStaticMap_whenUpdated_thenCorrect() {
+        
+        MapInitializer.articleMapOne.put("NewArticle1", "Convert array to List");
+        
+        assertEquals(MapInitializer.articleMapOne.get("NewArticle1"), "Convert array to List");
+        
+    }
+    
+    @Test(expected=UnsupportedOperationException.class)
+    public void givenSingleTonMap_whenEntriesAdded_throwsException() {
+        
+        Map<String, String> map = MapInitializer.createSingletonMap();
+        map.put("username2", "password2");
+    }
+
+}