public void ShouldRemoveDuplicates() { CityListManager listManager = new CityListManager(); var city1 = new City("Karpacz"); var city2 = new City("Wieleń"); var city3 = new City("Warszawa"); var city4 = new City("Karpacz"); var city5 = new City("Wieleń"); listManager.AddElement(city1); listManager.AddElement(city2); listManager.AddElement(city3); listManager.AddElement(city4); listManager.AddElement(city5); var result1 = listManager.CountElements(); listManager.RemoveDuplicates(new CitiesComparer()); var result2 = listManager.CountElements(); Assert.AreEqual(result2, 3); }