public void FilterNumberStartsWithTest()
{
//Arrange
List <Message> messages = new List <Message>();
messages.Add(new Message("+3801", "+38 777", $"Message #1"));
messages.Add(new Message("+3802", "+38 777", $"Message #2"));
messages.Add(new Message("+3802", "+38 777", $"Message #3"));
messages.Add(new Message("+3803", "+38 777", $"Message #4"));
messages.Add(new Message("+3802", "+38 777", $"Message #5"));
string expectedResult = "+3801";
//Act
MessageFilter messageFilter = new MessageFilter();
List <Message> filteredMessages = messageFilter.NumberStartsWith(messages, "+3801");
//Assert
Assert.AreEqual(expectedResult, filteredMessages[0].SenderNumber);
}