refactoring: update cd test naming

src/builtins/cd.rs

@@ -21,12 +21,12 @@ mod tests {
     use std::path::Path;
 
     #[test]
-    fn cd_current() {
+    fn test_cd_current() {
         assert_eq!(Cd.execute(vec![".".to_string()]), Ok(()))
     }
 
     #[test]
-    fn cd_not_existent() {
+    fn test_cd_not_existent() {
         // find a path which does not exists
         let mut path = Path::new("test").to_path_buf();
         while path.exists() {