Diagnose when test features are missing
diff --git a/tests/test_lit.rs b/tests/test_lit.rs
index b0e4004..2cdc7dc 100644
--- a/tests/test_lit.rs
+++ b/tests/test_lit.rs
@@ -10,6 +10,8 @@
 extern crate quote;
 extern crate syn;
 
+mod features;
+
 use proc_macro2::{TokenStream, TokenTree};
 use quote::ToTokens;
 use std::str::FromStr;