@Test
public void
it_selects_two_different_positions() {

   assertThat(new Board(
     l(B, W, W, B),
     l(W, B, W, W),
     l(_, W, B, W),
     l(_, W, W, B)).legalMovesFor(B))
     .containsExactly(position(2, 0), position(3, 0));
}