test: center|horizontal|vertical

src/utils.rs

@@ -23,3 +23,54 @@ pub fn center(base_area: Rect, horizontal: Constraint, vertical: Constraint) ->
     let area = center_horizontal(base_area, horizontal);
     center_vertical(area, vertical)
 }
+
+#[cfg(test)]
+mod tests {
+
+    use super::*;
+    use ratatui::{buffer::Buffer, layout::Rect, text::Span, widgets::Widget};
+
+    #[test]
+    fn test_center() {
+        let l = Span::raw("hello!");
+        let mut b = Buffer::empty(Rect::new(0, 0, 10, 3));
+        let area = center(
+            b.area,
+            Constraint::Length(l.width() as u16),
+            Constraint::Length(1),
+        );
+        l.render(area, &mut b);
+        #[rustfmt::skip]
+        let expected = Buffer::with_lines([
+            "          ",
+            "  hello!  ",
+            "          ",
+        ]);
+        assert_eq!(b, expected);
+    }
+
+    #[test]
+    fn test_center_horizontal() {
+        let l = Span::raw("hello!");
+        let mut b = Buffer::empty(Rect::new(0, 0, 10, 1));
+        let area = center_horizontal(b.area, Constraint::Length(l.width() as u16));
+        l.render(area, &mut b);
+        let expected = Buffer::with_lines(["  hello!  "]);
+        assert_eq!(b, expected);
+    }
+
+    #[test]
+    fn test_center_vertical() {
+        let l = Span::raw("hello vertical");
+        let mut b = Buffer::empty(Rect::new(0, 0, 20, 3));
+        let area = center_vertical(b.area, Constraint::Length(1));
+        l.render(area, &mut b);
+        #[rustfmt::skip]
+        let expected = Buffer::with_lines([
+            "                    ",
+            "hello vertical      ",
+            "                    ",
+        ]);
+        assert_eq!(b, expected);
+    }
+}