Add test config::test::language::with_encoding

src/config.rs

@@ -700,6 +700,15 @@ mod test {
             );
         }
 
+        #[test]
+        fn with_encoding() {
+            let lang_list = get_languages(Some("de_DE.UTF-8"), None);
+            assert_eq!(
+                lang_list,
+                [Language("de_DE"), Language("de"), Language("en")]
+            );
+        }
+
         #[test]
         fn ignore_posix_and_c() {
             let lang_list = get_languages(Some("POSIX"), None);