public static void CallHistoryTest()
{
GSM testGSM = GSM.IPhone4s;
testGSM.AddCall("0999-999-999", 2.3);
testGSM.AddCall("0888-999-999", 12.4);
testGSM.AddCall("0777-999-999", 4.34);
testGSM.AddCall("0666-999-999", 8.2);
testGSM.AddCall("0555-999-999", 11.2);
Console.WriteLine("-------Showing added calls--------");
testGSM.ShowCallHistory();
Console.WriteLine("------Calculating total price for calls------");
double totalCallPrice = testGSM.CalculateCallsTotalPrice();
Console.WriteLine("{0:C}", totalCallPrice);
Console.WriteLine("----Removing longest call and recalculating-----");
testGSM.RemoveLongestCallEntry();
testGSM.ShowCallHistory();
totalCallPrice = testGSM.CalculateCallsTotalPrice();
Console.WriteLine("{0:C}", totalCallPrice);
Console.WriteLine("----Clearing call history-----");
testGSM.ClearCallHistory();
testGSM.ShowCallHistory();
}