fix the order when number of cases exceeds 10
diff --git a/parameterized/parameterized.py b/parameterized/parameterized.py
index 1d83404..58a8137 100644
--- a/parameterized/parameterized.py
+++ b/parameterized/parameterized.py
@@ -424,8 +424,9 @@
             frame_locals = frame[0].f_locals
 
             paramters = cls.input_as_callable(input)()
+            digit = len(str(len(paramters) - 1))
             for num, p in enumerate(paramters):
-                name = name_func(f, num, p)
+                name = name_func(f, "{1:0>{0}}".format(digit, num), p)
                 frame_locals[name] = cls.param_as_standalone_func(p, f, name)
                 frame_locals[name].__doc__ = doc_func(f, num, p)