diff --git a/core-java-modules/core-java-lang-3/src/test/java/com/baeldung/isinstancevsisassignablefrom/IsInstanceIsAssignableFromUnitTest.java b/core-java-modules/core-java-lang-3/src/test/java/com/baeldung/isinstancevsisassignablefrom/IsInstanceIsAssignableFromUnitTest.java
index e0ad264797..3e4ee0a1bb 100644
--- a/core-java-modules/core-java-lang-3/src/test/java/com/baeldung/isinstancevsisassignablefrom/IsInstanceIsAssignableFromUnitTest.java
+++ b/core-java-modules/core-java-lang-3/src/test/java/com/baeldung/isinstancevsisassignablefrom/IsInstanceIsAssignableFromUnitTest.java
@@ -6,57 +6,80 @@ import static org.junit.Assert.assertTrue;
 import org.junit.Test;
 
 public class IsInstanceIsAssignableFromUnitTest {
-    
+
     @Test
-    public void whenUsingIsInstanceProperly_desiredResultsHappen() {
+    public void whenUsingInstanceOfProperly_thenDesiredResultsHappen() {
+        Shape shape = new Triangle();
+        Triangle triangle = new Triangle();
+        IsoscelesTriangle isoscelesTriangle = new IsoscelesTriangle();
+        Shape nonspecificShape = null;
+
+        assertTrue(shape instanceof Shape);
+        assertTrue(triangle instanceof Shape);
+        assertTrue(isoscelesTriangle instanceof Shape);
+        assertFalse(nonspecificShape instanceof Shape);
+
+        assertTrue(shape instanceof Triangle);
+        assertTrue(triangle instanceof Triangle);
+        assertTrue(isoscelesTriangle instanceof Triangle);
+        assertFalse(nonspecificShape instanceof Triangle);
+
+        assertFalse(shape instanceof IsoscelesTriangle);
+        assertFalse(triangle instanceof IsoscelesTriangle);
+        assertTrue(isoscelesTriangle instanceof IsoscelesTriangle);
+        assertFalse(nonspecificShape instanceof IsoscelesTriangle);
+    }
+
+    @Test
+    public void whenUsingIsInstanceProperly_thenDesiredResultsHappen() {
         Shape shape = new Triangle();
         Triangle triangle = new Triangle();
         IsoscelesTriangle isoscelesTriangle = new IsoscelesTriangle();
         Triangle isoscelesTriangle2 = new IsoscelesTriangle();
         Shape nonspecificShape = null;
-        
+
         assertTrue(Shape.class.isInstance(shape));
         assertTrue(Shape.class.isInstance(triangle));
         assertTrue(Shape.class.isInstance(isoscelesTriangle));
         assertTrue(Shape.class.isInstance(isoscelesTriangle2));
         assertFalse(Shape.class.isInstance(nonspecificShape));
-        
+
         assertTrue(Triangle.class.isInstance(shape));
         assertTrue(Triangle.class.isInstance(triangle));
         assertTrue(Triangle.class.isInstance(isoscelesTriangle));
         assertTrue(Triangle.class.isInstance(isoscelesTriangle2));
-        
+
         assertFalse(IsoscelesTriangle.class.isInstance(shape));
         assertFalse(IsoscelesTriangle.class.isInstance(triangle));
         assertTrue(IsoscelesTriangle.class.isInstance(isoscelesTriangle));
-        assertTrue(IsoscelesTriangle.class.isInstance(isoscelesTriangle2));        
+        assertTrue(IsoscelesTriangle.class.isInstance(isoscelesTriangle2));
     }
-    
+
     @Test
-    public void whenUsingIsAssignableFromProperly_desiredResultsHappen() {
+    public void whenUsingIsAssignableFromProperly_thenDesiredResultsHappen() {
         Shape shape = new Triangle();
         Triangle triangle = new Triangle();
         IsoscelesTriangle isoscelesTriangle = new IsoscelesTriangle();
         Triangle isoscelesTriangle2 = new IsoscelesTriangle();
-        
+
         assertFalse(shape.getClass().isAssignableFrom(Shape.class));
         assertTrue(shape.getClass().isAssignableFrom(shape.getClass()));
         assertTrue(shape.getClass().isAssignableFrom(triangle.getClass()));
         assertTrue(shape.getClass().isAssignableFrom(isoscelesTriangle.getClass()));
         assertTrue(shape.getClass().isAssignableFrom(isoscelesTriangle2.getClass()));
-        
+
         assertFalse(triangle.getClass().isAssignableFrom(Shape.class));
         assertTrue(triangle.getClass().isAssignableFrom(shape.getClass()));
         assertTrue(triangle.getClass().isAssignableFrom(triangle.getClass()));
         assertTrue(triangle.getClass().isAssignableFrom(isoscelesTriangle.getClass()));
         assertTrue(triangle.getClass().isAssignableFrom(isoscelesTriangle2.getClass()));
-        
+
         assertFalse(isoscelesTriangle.getClass().isAssignableFrom(Shape.class));
         assertFalse(isoscelesTriangle.getClass().isAssignableFrom(shape.getClass()));
         assertFalse(isoscelesTriangle.getClass().isAssignableFrom(triangle.getClass()));
         assertTrue(isoscelesTriangle.getClass().isAssignableFrom(isoscelesTriangle.getClass()));
         assertTrue(isoscelesTriangle.getClass().isAssignableFrom(isoscelesTriangle2.getClass()));
-        
+
         assertFalse(isoscelesTriangle2.getClass().isAssignableFrom(Shape.class));
         assertFalse(isoscelesTriangle2.getClass().isAssignableFrom(shape.getClass()));
         assertFalse(isoscelesTriangle2.getClass().isAssignableFrom(triangle.getClass()));
@@ -64,4 +87,31 @@ public class IsInstanceIsAssignableFromUnitTest {
         assertTrue(isoscelesTriangle2.getClass().isAssignableFrom(isoscelesTriangle2.getClass()));
     }
 
+    @Test(expected = NullPointerException.class)
+    public void whenUsingNull_thenDesiredResultsHappen() {
+        assertFalse(null instanceof Shape);
+        assertFalse(Shape.class.isInstance(null));
+        assertFalse(Shape.class.isAssignableFrom(null)); // NullPointerException
+    }
+
+    @Test
+    public void whenUsingPrimitiveType_thenDesiredResultsHappen() {
+        //assertFalse(10 instanceof int); // illegal
+        assertFalse(int.class.isInstance(10));
+        assertTrue(Integer.class.isInstance(10));
+        assertTrue(int.class.isAssignableFrom(int.class));
+        assertFalse(float.class.isAssignableFrom(int.class));
+    }
+
+    @Test
+    public void whenUsingClassInstanceVariable_thenDesiredResultsHappen() {
+        Shape shape = new Triangle();
+        Triangle triangle = new Triangle();
+        Class<?> clazz = shape.getClass();
+
+        //assertFalse(triangle instanceof clazz); // illegal
+        assertTrue(clazz.isInstance(triangle));
+        assertTrue(clazz.isAssignableFrom(triangle.getClass()));
+    }
+
 }