Add additional unit tests to show how lazy loading is working with reflection

lazy-loading/src/test/java/com/iluwatar/lazy/loading/HolderThreadSafeTest.java

@@ -0,0 +1,41 @@
+package com.iluwatar.lazy.loading;
+
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+
+/**
+ * Using reflection this test shows that the heavy field is not instantiated until the method getHeavy is called
+ *
+ * Created by jones on 11/10/2015.
+ */
+public class HolderThreadSafeTest {
+
+    @Test
+    public void test() throws IllegalAccessException {
+        HolderThreadSafe hts = new HolderThreadSafe();
+
+        {//first call is null
+            Field[] f = HolderThreadSafe.class.getDeclaredFields();
+            assertEquals("One field only in HolderThreadSafe", 1, f.length);
+            f[0].setAccessible(true);
+
+            assertNull(f[0].get(hts));
+        }
+
+        // now it is lazily loaded
+        hts.getHeavy();
+
+        {//now it is not null - call via reflection so that the test is the same before and after
+            Field[] f = HolderThreadSafe.class.getDeclaredFields();
+            assertEquals("One field only in HolderThreadSafe", 1, f.length);
+            f[0].setAccessible(true);
+
+            assertNotNull(f[0].get(hts));
+        }
+    }
+}