increase CharRange test coverage as reported by clover

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/lang/trunk@234400 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/test/org/apache/commons/lang/CharRangeTest.java b/src/test/org/apache/commons/lang/CharRangeTest.java
index babe929..381f870 100644
--- a/src/test/org/apache/commons/lang/CharRangeTest.java
+++ b/src/test/org/apache/commons/lang/CharRangeTest.java
@@ -348,6 +348,15 @@
         assertEquals(true, notbd.contains(notae));
     }
     
+    public void testContainsNullArg() {
+        CharRange range = new CharRange('a');
+        try {
+            boolean contains = range.contains(null);
+        } catch(IllegalArgumentException e) {
+            assertEquals("The Range must not be null", e.getMessage());
+        }
+    }
+    
     //-----------------------------------------------------------------------    
     public void testSerialization() {
         CharRange range = new CharRange('a');