public void ItShouldIncreaseStockWithNegativeValue()
{
const string beerLabel = "Sample Label";
const string beerDescription = "Sample Description";
const int beerStock = 250;
var beer = new Beer(null, beerLabel, beerDescription, beerStock);
beer.IncreaseStock(-5);
Assert.Equal(255, beer.Stock.Value);
}