/**
     * Make sure that makeNewUnit do not put a new unit out of map.
     */
    @Test
    public void shouldTestThatMakeNewUnitDoNotPutUnitOutOFMapButIncreaseTreasury() {
        assertThat(game.getCityAt(redCityPosition).getOwner(),is(Player.RED));

        int startingTreasury = ((CityImpl) game.getCityAt(redCityPosition)).getTreasurySize();
        assertThat("Start with 0", startingTreasury, is(0));

        GameHelperMethods.numberOfEndOfTurn(game,20);
        int currentTreasury = ((CityImpl) game.getCityAt(redCityPosition)).getTreasurySize();
        assertThat("Should have 10*6 = 60 = 6_Archer = 0 treasury left", currentTreasury, is(0));

        assertThat("Red city has a new Archer at (0,0) because of Archer (2,0) and Ocean (1,0)",
                game.getUnitAt(new Position(0, 0)).getTypeString(), is(GameConstants.ARCHER));

        assertThat(((CityImpl) game.getCityAt(redCityPosition)).getTreasurySize(),is(0));

        GameHelperMethods.numberOfEndOfTurn(game,4);
        assertThat("Instead of new unit out of map it increase treasurySize",
                ((CityImpl) game.getCityAt(redCityPosition)).getTreasurySize(),is(12));
        GameHelperMethods.numberOfEndOfTurn(game,2);
        assertThat("Instead of new unit out of map it increase treasurySize",
                ((CityImpl) game.getCityAt(redCityPosition)).getTreasurySize(),is(18));

    }




===============================================================================================



private void tryingToBuyUnitsWithProduction(Position p) {
        int treasurySize = getCurrentTreasurySize(p);
        String productionUnitType = getCityAt(p).getProduction();
        int priceForProductionFocus = matchProductionFocusWithPriceOfUnit(productionUnitType);

        // If we have money enough
        if (treasurySize >= priceForProductionFocus) {

            Position[] freePosition = p.getValidPositions();
            for (Position position : freePosition) {
                if (isTileFree(position)) {
                    unitWorld.put(position, new UnitImpl(productionUnitType, getPlayerInTurn()));
                    setTreasurySize(p, treasurySize - priceForProductionFocus);
                    break;
                }
            }
        }
    }