[board] Implement a move generator test for a single king

board/src/move_generator/move_generator.rs

@@ -40,3 +40,40 @@ impl<'a> Moves<'a> {
             .cloned()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::{piece, position, r#move::AlgebraicMoveFormatter, Move, MoveBuilder, Square};
+    use std::collections::HashSet;
+
+    #[test]
+    fn one_king() {
+        let pos = position![
+            White King on D3,
+            Black King on H6,
+        ];
+
+        let expected_moves = HashSet::from_iter([
+            MoveBuilder::new(piece!(White King), Square::D3, Square::D4).build(),
+            MoveBuilder::new(piece!(White King), Square::D3, Square::E4).build(),
+            MoveBuilder::new(piece!(White King), Square::D3, Square::E3).build(),
+            MoveBuilder::new(piece!(White King), Square::D3, Square::E2).build(),
+            MoveBuilder::new(piece!(White King), Square::D3, Square::D2).build(),
+            MoveBuilder::new(piece!(White King), Square::D3, Square::C2).build(),
+            MoveBuilder::new(piece!(White King), Square::D3, Square::C3).build(),
+            MoveBuilder::new(piece!(White King), Square::D3, Square::C4).build(),
+        ]);
+
+        let generated_moves: HashSet<Move> = pos.moves().iter().collect();
+
+        assert_eq!(
+            generated_moves,
+            expected_moves,
+            "{:?}",
+            generated_moves
+                .symmetric_difference(&expected_moves)
+                .map(|m| format!("{}", AlgebraicMoveFormatter::new(&m, &pos)))
+                .collect::<Vec<String>>()
+        );
+    }
+}