Add test for StringBuilder

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1391116 13f79535-47bb-0310-9956-ffa450edef68

src/test/java/org/apache/commons/lang3/text/StrBuilderAppendInsertTest.java

@@ -112,6 +112,9 @@ public class StrBuilderAppendInsertTest {
 
         sb.append((CharSequence) "Seq");
         assertEquals("foobazyesSeq", sb.toString());
+
+        sb.append(new StringBuilder("bld")); // Check it supports StringBuilder
+        assertEquals("foobazyesSeqbld", sb.toString());
     }
 
     //-----------------------------------------------------------------------