Let's start with the command argument, that only has the f (forwards) character:

public void whenReceiveCommandsFThenForward() {
  Location expected = location.copy();
  expected.forward();
  ship.receiveCommands("f");
  assertEquals(ship.getLocation(), expected);
}

This specification is almost the same as the whenMoveForwardThenForward specification except that, this time, we're invoking the ship.receiveCommands("f") method.