Add test for double substitution from XLogger

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/branches/BRANCH_2_0_EXPERIMENTAL/rgoers@1172183 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/slf4j-impl/src/test/java/org/apache/logging/slf4j/LoggerTest.java b/slf4j-impl/src/test/java/org/apache/logging/slf4j/LoggerTest.java
index 3cd635c..2807fff 100644
--- a/slf4j-impl/src/test/java/org/apache/logging/slf4j/LoggerTest.java
+++ b/slf4j-impl/src/test/java/org/apache/logging/slf4j/LoggerTest.java
@@ -142,8 +142,8 @@
     public void doubleSubst() {
         logger.debug("Hello, {}", "Log4j {}");
         verify("List", "o.a.l.s.LoggerTest Hello, Log4j {} MDC{}\n");
-        //xlogger.debug("Hello, {}", "Log4j {}");
-        //verify("List", "o.a.l.s.LoggerTest Hello, Log4j {} MDC{}\n");
+        xlogger.debug("Hello, {}", "Log4j {}");
+        verify("List", "o.a.l.s.LoggerTest Hello, Log4j Log4j {} MDC{}\n");
     }
 
     @Test