Simplify Leaf and its sub-classes.

Change-Id: I711db26bedee2bebdd39ffd8b637fa8918c16ff9
diff --git a/tests/wscript b/tests/wscript
index bc847a9..d1a61ba 100644
--- a/tests/wscript
+++ b/tests/wscript
@@ -8,7 +8,7 @@
         target='unit-tests-main',
         name='unit-tests-main',
         features='cxx',
-        source=bld.path.ant_glob(['*.cpp']),
+        source=bld.path.ant_glob(['main.cpp']),
         use='ChronoSync',
         )