public void FilterFlightsByAirportPair_MultipleAirportPairs_ReturnsFilteredFlights() { // Arrange var firstFlight = new Flight { DepartureAirportCode = "SEA", ArrivalAirportCode = "PHX" }; var secondFlight = new Flight { DepartureAirportCode = "SEA", ArrivalAirportCode = "PHX" }; var thirdFlight = new Flight { DepartureAirportCode = "PHX", ArrivalAirportCode = "LAX" }; var initialFlights = new List <Flight> { firstFlight, secondFlight, thirdFlight }; var sortingHelper = new SortingHelper(); // Act var filteredFlights = sortingHelper.FilterFlightsByAirportPair("SEA", "PHX", initialFlights); // Assert filteredFlights.Count.ShouldBe(2); filteredFlights.ShouldNotContain(thirdFlight); }