public void TestSelectManyWhenExists()
{
var productList = new ProductsList().GetProducts();
Func <ProductsList.Product, List <ProductsList.Ingredient> > MyFunc = x => x.Ingredients;
var selectedIngredients = LinqFunctions.SelectMany(productList, MyFunc);
var enumerator = selectedIngredients.GetEnumerator();
int counter = 0;
while (enumerator.MoveNext())
{
counter++;
}
Assert.Equal(7, counter);
}