Add a test to CFG, to see if it panics on clearly invalid garbage data

src/cfg.rs

@@ -131,6 +131,14 @@ mod tests {
         read(d).unwrap()
     }
 
+    fn common_setup_invalid() -> ByteBuffer {
+        let mut d = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
+        d.push("resources/tests");
+        d.push("random");
+
+        read(d).unwrap()
+    }
+
     #[test]
     fn basic_parsing() {
         let cfg = common_setup();
@@ -150,4 +158,12 @@ mod tests {
 
         assert_eq!(modified_cfg, cfg_buffer);
     }
+
+    #[test]
+    fn test_invalid() {
+        let cfg = common_setup_invalid();
+
+        // Feeding it invalid data should not panic
+        ConfigFile::from_existing(&cfg);
+    }
 }