improve test case
diff --git a/java_gen/templates/of_interface.java b/java_gen/templates/of_interface.java
index a515ad1..18e2cf1 100644
--- a/java_gen/templates/of_interface.java
+++ b/java_gen/templates/of_interface.java
@@ -27,6 +27,7 @@
//::
//:: import itertools
//:: import re
+//:: import os
//:: include('_copyright.java')
//:: include('_autogen.java')
@@ -39,6 +40,10 @@
//:: for prop in msg.members:
${prop.java_type.public_type} ${prop.getter_name}()${ "" if prop.is_universal else " throws UnsupportedOperationException"};
//:: #endfor
+//:: if os.path.exists("%s/custom/interface/%s.java" % (template_dir, msg.name)):
+//:: include("custom/interface/%s.java" % msg.name, msg=msg)
+//:: #endif
+
void writeTo(ChannelBuffer channelBuffer);