modes:mod: refactor Hand

Hand now requires Ord to be implemented, and test_footstool is a bit
more precise than test_footstool_non_reflexivity.

src/modes/mod.rs

@@ -9,39 +9,53 @@ pub enum Footstool {
     Full,
 }
 
-pub trait Hand {
-    /** Given two instances of a Hand (`self` and `other`), verify if `self`
-    footstools `other`.
-     */
-    fn footstool(&self, other: &Self) -> Footstool;
-
+pub trait Hand: Ord {
     // Only need to implement is_proper.
     fn is_proper(&self) -> bool;
 
     fn is_improper(&self) -> bool {
         !self.is_proper()
     }
+
+    /** Given two instances of a Hand (`self` and `other`), verify if `self`
+    footstools `other`.
+     */
+    fn footstool(&self, other: &Self) -> Footstool;
 }
 
 #[cfg(test)]
 mod tests {
+    use std::fmt::Display;
+
     use super::*;
 
-    /** Given two hands, assert that their footstool condition is non-reflexive.
-    Return the results of the two footstool checks (x on y, y on x).
+    /** Given two hands, assert that applying a footstool both ways fits a
+    recognised pattern.  Return the results of the two footstool checks (x on y,
+    y on x).
      */
-    pub fn test_footstool_non_reflexivity<T: Hand + Copy>(
-        x: &T,
-        y: &T,
-    ) -> (Footstool, Footstool) {
+    pub fn test_footstool<T>(x: &T, y: &T) -> (Footstool, Footstool)
+    where
+        T: Hand + Copy + Display,
+    {
         let res1 = x.footstool(y);
         let res2 = y.footstool(x);
-        matches!(
-            (res1, res2),
-            (Footstool::None, Footstool::None)
+        assert!(
+            match (res1, res2) {
+                // Default patterns we'd expect
+                (Footstool::Half, Footstool::None)
                 | (Footstool::None, Footstool::Half)
-                | (Footstool::Half, Footstool::None)
-                | (Footstool::Full, Footstool::Full)
+                | (Footstool::None, Footstool::None)
+                    => true,
+
+                // Patterns that require an exact examination to be certain
+                (Footstool::Full, Footstool::Full) => x == y,
+                _ => true,
+            },
+            "Expected footstool on {}, {} ({:?}, {:?}) to match a recognised pattern",
+            x,
+            y,
+            res1,
+            res2
         );
         (res1, res2)
     }