Add layout tests

Author: Martan03

tests/layout.rs

@@ -0,0 +1,72 @@
+#[cfg(test)]
+mod tests {
+    use termal::formatc;
+    use termint::{
+        buffer::Buffer,
+        enums::Color,
+        geometry::{Constraint, Rect},
+        widgets::{cache::Cache, Layout, Widget},
+    };
+
+    #[test]
+    fn background_render() {
+        let rect = Rect::new(1, 1, 10, 5);
+        let mut buffer = Buffer::empty(rect);
+        let mut cache = Cache::new();
+
+        let layout = Layout::vertical().bg(Color::Red).into();
+        cache.diff(&layout);
+        layout.render(&mut buffer, Rect::new(3, 2, 6, 3), &mut cache);
+
+        let bg =
+            format!("{}      {}", Color::Red.to_bg(), Color::Default.to_bg());
+        let expected = formatc!(
+            "          \n  {bg}  \n  {bg}  \n  {bg}  \n          {'_}"
+        );
+        assert_eq!(buffer.to_string(), expected);
+    }
+
+    #[test]
+    fn padding_render() {
+        let rect = Rect::new(1, 1, 10, 5);
+        let mut buffer = Buffer::empty(rect);
+        let mut cache = Cache::new();
+
+        let mut layout = Layout::vertical().padding((1, 2, 2, 3));
+        layout.push(Layout::vertical().bg(Color::Red), Constraint::Fill(1));
+        let layout = layout.into();
+
+        cache.diff(&layout);
+        layout.render(&mut buffer, rect, &mut cache);
+
+        let bg =
+            format!("{}     {}", Color::Red.to_bg(), Color::Default.to_bg());
+        let expected = formatc!(
+            "          \n   {bg}  \n   {bg}  \n          \n          {'_}"
+        );
+        assert_eq!(buffer.to_string(), expected);
+    }
+
+    #[test]
+    fn center_render() {
+        let rect = Rect::new(1, 1, 10, 5);
+        let mut buffer = Buffer::empty(rect);
+        let mut cache = Cache::new();
+
+        let mut layout = Layout::horizontal().center();
+        let mut inner = Layout::vertical().center();
+        inner.push(Layout::vertical().bg(Color::Red), Constraint::Length(3));
+        layout.push(inner, Constraint::Length(2));
+
+        let layout = layout.into();
+        cache.diff(&layout);
+        layout.render(&mut buffer, rect, &mut cache);
+
+        let bg = format!("{}  {}", Color::Red.to_bg(), Color::Default.to_bg());
+        let expected = formatc!(
+            "          \n    {bg}    \n    {bg}    \n    {bg}    \
+            \n          {'_}"
+        );
+        assert_eq!(buffer.to_string(), expected);
+    }
+}