test: add cd not existent directory test

src/builtins/cd.rs

@@ -18,9 +18,25 @@ impl Builtin for Cd {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::path::Path;
 
     #[test]
     fn cd_current() {
         assert_eq!(Cd.execute(vec![".".to_string()]), Ok(()))
     }
+
+    #[test]
+    fn cd_not_existent() {
+        // find a path which does not exists
+        let mut path = Path::new("test").to_path_buf();
+        while path.exists() {
+            path.set_file_name(format!(
+                "{}test",
+                path.file_name().unwrap_or_default().to_string_lossy()
+            ))
+        }
+
+        // No such file or directory (os error 2)
+        assert_ne!(Cd.execute(vec![path.to_string_lossy().to_string()]), Ok(()))
+    }
 }