add test ensuring that isNotEmpty(...) is the negation of isEmpty(...)

Author: kwin

src/test/java/org/codehaus/plexus/util/xml/Xpp3DomUtilsTest.java

@@ -127,6 +127,15 @@ public void testOverwriteDominantBlankValue() throws XmlPullParserException, IOE
         assertEquals( " ", mergeResult.getValue() );
     }
 
+    @Test
+    public void testIsNotEmptyNegatesIsEmpty()
+    {
+        assertEquals( !Xpp3DomUtils.isEmpty( null ), Xpp3DomUtils.isNotEmpty( null ) );
+        assertEquals( !Xpp3DomUtils.isEmpty( "" ), Xpp3DomUtils.isNotEmpty( "" ) );
+        assertEquals( !Xpp3DomUtils.isEmpty( " " ), Xpp3DomUtils.isNotEmpty( " " ) );
+        assertEquals( !Xpp3DomUtils.isEmpty( "someValue" ), Xpp3DomUtils.isNotEmpty( "someValue" ) );
+    }
+
     private static class FixedInputLocationBuilder
         implements Xpp3DomBuilder.InputLocationBuilder
     {