public void GetQuote_bycurrency_valid() { // MOCK var quotes = new List <Quote> { new Quote { Currency = "usd" }, new Quote { Currency = "can" }, new Quote { Currency = "usd" } }; _quoteRepository.GetQuotes().Returns(quotes); // Execute var filter = new QuotesFilter(); filter.AddFilterByCurrency("usd"); var result = _sut.GetQuotes().ToList(); result = _sut.FilterQuotes(result, filter).ToList(); // Assert Assert.AreEqual(2, result.Count); Assert.AreEqual(0, result.Count(x => x.Currency == "can")); Assert.IsTrue(result.Count == 2); }