add tests for serde support

tests/serde.rs

@@ -0,0 +1,47 @@
+#![cfg(feature = "serde")]
+
+use tui_textarea::{CursorMove, Input, Key, Scrolling};
+
+#[test]
+fn test_serde_key() {
+    let k = Key::Char('a');
+    let s = serde_json::to_string(&k).unwrap();
+    assert_eq!(s, r#"{"Char":"a"}"#);
+    let d: Key = serde_json::from_str(&s).unwrap();
+    assert_eq!(d, k);
+}
+
+#[test]
+fn test_serde_input() {
+    let i = Input {
+        key: Key::Char('a'),
+        ctrl: true,
+        alt: false,
+        shift: true,
+    };
+    let s = serde_json::to_string(&i).unwrap();
+    assert_eq!(
+        s,
+        r#"{"key":{"Char":"a"},"ctrl":true,"alt":false,"shift":true}"#,
+    );
+    let d: Input = serde_json::from_str(&s).unwrap();
+    assert_eq!(d, i);
+}
+
+#[test]
+fn test_serde_scrolling() {
+    let scroll = Scrolling::Delta { rows: 1, cols: 2 };
+    let s = serde_json::to_string(&scroll).unwrap();
+    assert_eq!(s, r#"{"Delta":{"rows":1,"cols":2}}"#);
+    let d: Scrolling = serde_json::from_str(&s).unwrap();
+    assert_eq!(d, scroll);
+}
+
+#[test]
+fn test_serde_cursor_move() {
+    let c = CursorMove::Forward;
+    let s = serde_json::to_string(&c).unwrap();
+    assert_eq!(s, r#""Forward""#);
+    let d: CursorMove = serde_json::from_str(&s).unwrap();
+    assert_eq!(d, c);
+}