diff --git a/native/src/widget/pane_grid/axis.rs b/native/src/widget/pane_grid/axis.rs
index 7181f9bf..f8c7b661 100644
--- a/native/src/widget/pane_grid/axis.rs
+++ b/native/src/widget/pane_grid/axis.rs
@@ -54,3 +54,90 @@ impl Axis {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn split_horizontal() {
+        let a = Axis::Horizontal;
+        // rectangle height, spacing, top height, bottom y, bottom height
+        let cases = vec![
+            // Even height, even spacing
+            (10.0, 2.0, 4.0, 6.0, 4.0),
+            // Odd height, even spacing
+            (9.0, 2.0, 4.0, 6.0, 3.0),
+            // Even height, odd spacing
+            (10.0, 1.0, 5.0, 6.0, 4.0),
+            // Odd height, odd spacing
+            (9.0, 1.0, 4.0, 5.0, 4.0),
+        ];
+        for case in cases {
+            let (h0, spacing, h1_top, y_bottom, h1_bottom) = case;
+            let r = Rectangle {
+                x: 0.0,
+                y: 0.0,
+                width: 10.0,
+                height: h0,
+            };
+            let (top, bottom) = a.split(&r, 0.5, spacing);
+            assert_eq!(
+                top,
+                Rectangle {
+                    height: h1_top,
+                    ..r
+                }
+            );
+            assert_eq!(
+                bottom,
+                Rectangle {
+                    y: y_bottom,
+                    height: h1_bottom,
+                    ..r
+                }
+            );
+        }
+    }
+
+    #[test]
+    fn split_vertical() {
+        let a = Axis::Vertical;
+        // rectangle width, spacing, left width, right x, right width
+        let cases = vec![
+            // Even width, even spacing
+            (10.0, 2.0, 4.0, 6.0, 4.0),
+            // Odd width, even spacing
+            (9.0, 2.0, 4.0, 6.0, 3.0),
+            // Even width, odd spacing
+            (10.0, 1.0, 5.0, 6.0, 4.0),
+            // Odd width, odd spacing
+            (9.0, 1.0, 4.0, 5.0, 4.0),
+        ];
+        for case in cases {
+            let (w0, spacing, w1_left, x_right, w1_right) = case;
+            let r = Rectangle {
+                x: 0.0,
+                y: 0.0,
+                width: w0,
+                height: 10.0,
+            };
+            let (left, right) = a.split(&r, 0.5, spacing);
+            assert_eq!(
+                left,
+                Rectangle {
+                    width: w1_left,
+                    ..r
+                }
+            );
+            assert_eq!(
+                right,
+                Rectangle {
+                    x: x_right,
+                    width: w1_right,
+                    ..r
+                }
+            );
+        }
+    }
+}