@Test
 public void testChangeDirection() {
   assertEquals("armyDirection must be 1", 1, osa.getArmyDirection());
   osa.changeDirection();
   assertEquals(
       "armyDirection (after call of change direction method) must be -1",
       -1,
       osa.getArmyDirection());
   osa.changeDirection();
   assertEquals("armyDirection return to 1", 1, osa.getArmyDirection());
 }
 @Test
 public void testGetXOffset() {
   BattleField bf = null;
   try {
     bf = new BattleField("es-in.txt");
   } catch (IllegalElementException e) {
     e.printStackTrace();
   } catch (IllegalPositionException e) {
     e.printStackTrace();
   }
   bf.setColumns(5);
   assertEquals("Entry in first if", 5 - (2 + 1), osa.getXOffset());
   osa.changeDirection();
   assertEquals("after changed direction", -2, osa.getXOffset());
   osa.changeDirection(); // reset back because is static
 }
 @Test
 public void testToString() {
   assertEquals("String returned must be: A", "A", osa.toString());
 }
 @Test
 public void testGetYOffset() {
   assertEquals("Y of one step alien must return 0", 0, osa.getYOffset());
 }