public void FilterByBlueAndSmallReturn1() { // arrange ProductFilter filter = new ProductFilter(); IList<Product> products = BuildProducts(); // act var result = filter.ByColorAndSize(products, ProductColor.Blue, ProductSize.Small); // assert Assert.That(result.Count(), Is.EqualTo(1)); Assert.That(result, Has.All.Matches<Product>(x => x.Size == ProductSize.Small)); }