diff --git a/src/modes/mod.rs b/src/modes/mod.rs
index 4b38077..a29dd89 100644
--- a/src/modes/mod.rs
+++ b/src/modes/mod.rs
@@ -11,3 +11,22 @@ pub enum Footstool {
 pub trait Hand {
     fn footstool(&self, other: Self) -> Footstool;
 }
+
+mod tests {
+    use super::*;
+    pub fn test_non_reflexivity<T: Hand + Copy>(
+        x: &T,
+        y: &T,
+    ) -> (Footstool, Footstool) {
+        let res1 = x.footstool(*y);
+        let res2 = y.footstool(*x);
+        assert!(match (res1, res2) {
+            (Footstool::None, Footstool::None)
+            | (Footstool::None, Footstool::Half)
+            | (Footstool::Half, Footstool::None)
+            | (Footstool::Full, Footstool::Full) => true,
+            _ => false,
+        });
+        (res1, res2)
+    }
+}