diff --git a/src/models.rs b/src/models.rs
index 4aa497d..3acf60d 100644
--- a/src/models.rs
+++ b/src/models.rs
@@ -48,3 +48,21 @@ impl Default for Pos {
         Self::new(0, 1, 1)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn valid_invalid_chars() {
+        let pos = Pos::default();
+
+        assert_eq!(Char::new('\0', pos), Err('\0'));
+        assert_eq!(Char::new('\t', pos), Err('\t'));
+        assert_eq!(Char::new('\r', pos), Err('\r'));
+
+        assert_eq!(Char::new(' ', pos), Ok(Char { value: ' ', pos }));
+        assert_eq!(Char::new('\n', pos), Ok(Char { value: '\n', pos }));
+        assert_eq!(Char::new('a', pos), Ok(Char { value: 'a', pos }));
+    }
+}