Add test that cells() can be equal for different rotation states

mino/src/srs.rs

@@ -193,4 +193,35 @@ mod test {
         assert_eq!(piece.loc.y, 1);
         assert_eq!(piece.loc.r, Rot::E);
     }
+
+    #[test]
+    fn test_srs_cells_eq() {
+        fn rotate(s: Shape, dir: input::Spin) -> Piece {
+            let mut piece = Piece::spawn(s);
+            input::rotate(&mut piece, Mat::EMPTY, dir).unwrap();
+            piece
+        }
+        for s in [Shape::S, Shape::Z, Shape::I] {
+            let cw = rotate(s, input::Spin::Cw);
+            let ccw = rotate(s, input::Spin::Ccw);
+            // rotation states differ
+            assert_ne!(cw.loc.r, ccw.loc.r, "shape={s:?}");
+            // cells() are equal after translating, since they occupy the same blocks
+            assert_eq!(cw.cells().translate(-1, 0), ccw.cells(), "shape={s:?}");
+        }
+    }
+
+    #[test]
+    fn test_o_cells_eq() {
+        fn cells(x: i16, y: i16, r: Rot) -> Cells<'static> {
+            Piece {
+                shape: Shape::O,
+                loc: Loc { x, y, r },
+            }
+            .cells()
+        }
+        assert_eq!(cells(0, 0, Rot::N), cells(0, 1, Rot::E));
+        assert_eq!(cells(0, 0, Rot::N), cells(1, 1, Rot::S));
+        assert_eq!(cells(0, 0, Rot::N), cells(1, 0, Rot::W));
+    }
 }