Better code usability and clear errors

src/main/java/org/codeartisans/junit/Assert.java

@@ -24,7 +24,11 @@
 import java.io.ObjectOutputStream;
 import java.io.Serializable;
 
+/**
+ * This class extends org.junit.Assert and augments provided static assertions.
+ */
 public final class Assert
+        extends org.junit.Assert
 {
 
     public static interface PostSerializationAssertions<T extends Serializable>
@@ -37,6 +41,10 @@ public static interface PostSerializationAssertions<T extends Serializable>
     public static <T extends Serializable> void assertSerializable( T tested, PostSerializationAssertions<T> assertions )
             throws IOException, ClassNotFoundException
     {
+        if ( tested == null ) {
+            throw new IllegalArgumentException( "Assert.assertSerializable tested argument was null" );
+        }
+
         // Serialize
         ByteArrayOutputStream out = new ByteArrayOutputStream();
         ObjectOutputStream oos = new ObjectOutputStream( out );
@@ -48,6 +56,7 @@ public static <T extends Serializable> void assertSerializable( T tested, PostSe
         InputStream in = new ByteArrayInputStream( pickled );
         ObjectInputStream ois = new ObjectInputStream( in );
         Object o = ois.readObject();
+        assertNotNull( o );
         // Cast
         @SuppressWarnings( "unchecked" )
         T copy = ( T ) o;