tic tac toe

src/lib.rs

@@ -1,17 +1,17 @@
 mod board;
 mod game;
-mod minmax;
+mod perfect;
 
 use std::io::Write;
 
 pub use board::{Board, Player, State};
-pub use minmax::PerfectPlayer;
+pub use perfect::PerfectPlayer;
 
-pub trait GamePlayer {
+pub trait GamePlayer: Default {
     fn next_move(&mut self, board: &mut Board, this_player: Player);
 }
 
-#[derive(Clone)]
+#[derive(Clone, Default)]
 pub struct GreedyPlayer;
 
 impl GamePlayer for GreedyPlayer {
@@ -21,7 +21,7 @@ impl GamePlayer for GreedyPlayer {
     }
 }
 
-#[derive(Clone)]
+#[derive(Clone, Default)]
 pub struct HumanPlayer;
 
 impl GamePlayer for HumanPlayer {
@@ -51,7 +51,7 @@ impl GamePlayer for HumanPlayer {
     }
 }
 
-#[derive(Clone)]
+#[derive(Clone, Default)]
 pub struct RandomPlayer;
 
 fn fun_random() -> u64 {
@@ -75,3 +75,34 @@ impl GamePlayer for RandomPlayer {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::{Board, GamePlayer, GreedyPlayer, PerfectPlayer, Player, RandomPlayer};
+
+    fn assert_win_ratio<X: GamePlayer, O: GamePlayer>(runs: u64, x_win_ratio: f64) {
+        let mut results = [0u64, 0, 0];
+
+        for _ in 0..runs {
+            let result = Board::default_play::<X, O>();
+            let idx = Player::as_u8(result);
+            results[idx as usize] += 1;
+        }
+
+        let total = results.iter().copied().sum::<u64>();
+
+        let ratio = (total as f64) / (results[0] as f64);
+        println!("{ratio} >= {x_win_ratio}");
+        assert!(ratio >= x_win_ratio);
+    }
+
+    #[test]
+    fn perfect_always_beats_greedy() {
+        assert_win_ratio::<PerfectPlayer, GreedyPlayer>(20, 1.0);
+    }
+
+    #[test]
+    fn perfect_beats_random() {
+        assert_win_ratio::<PerfectPlayer, RandomPlayer>(10, 0.95);
+    }
+}