test: cover multi-byte input in NBReader::try_read

Author: SAY-5

src/reader.rs

@@ -457,4 +457,20 @@ mod tests {
         assert_eq!(None, r.try_read());
         assert_eq!(None, r.try_read());
     }
+
+    #[test]
+    fn test_try_read_multibyte_byte() {
+        // bytes >= 0x80 decode to multi-byte chars in the buffer, so draining one byte used to panic
+        let f = io::Cursor::new("é");
+        let mut r = NBReader::new(f, Options::default());
+        let mut count = 0;
+        loop {
+            match r.try_read() {
+                Some(_) => count += 1,
+                None if count == "é".len() => break,
+                None => thread::sleep(time::Duration::from_millis(10)),
+            }
+        }
+        assert_eq!(count, "é".len());
+    }
 }