Add some actions unit tests

src/actions.rs

@@ -159,3 +159,57 @@ pub fn insert_newline(state: &mut State) {
     state.cursor.line += 1;
     state.cursor.column = 0;
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn state(src: &str) -> State {
+        State::from_str(None, src).unwrap()
+    }
+
+    #[test]
+    fn backspace_empty() {
+        let mut state = state("");
+        delete_char_backward(&mut state);
+    }
+
+    #[test]
+    fn append_on_newline() {
+        let mut state = state("test\ntest\n");
+        state.cursor.column = 4;
+        append_mode(&mut state);
+        assert_eq!(state.cursor.line, 1);
+        assert_eq!(state.cursor.column, 0);
+    }
+
+    #[test]
+    fn append_at_eof() {
+        let mut state = state("test\n");
+        state.cursor.column = 4;
+        append_mode(&mut state);
+        assert_eq!(state.cursor.line, 1);
+        assert_eq!(state.cursor.column, 0);
+    }
+
+    #[test]
+    fn move_line_up_preserve_column() {
+        let mut state = state("test\n\ntest\n");
+        state.cursor.line = 2;
+        state.cursor.column = 3;
+        move_line_up(&mut state);
+        move_line_up(&mut state);
+        assert_eq!(state.cursor.line, 0);
+        assert_eq!(state.cursor.column, 3);
+    }
+
+    #[test]
+    fn move_line_down_preserve_column() {
+        let mut state = state("test\n\ntest\n");
+        state.cursor.column = 3;
+        move_line_down(&mut state);
+        move_line_down(&mut state);
+        assert_eq!(state.cursor.line, 2);
+        assert_eq!(state.cursor.column, 3);
+    }
+}