public void AddBookReaderTest()
        {
            int beforeSize           = context.bookReaders.Count;
            var beforeLastBookReader = context.bookReaders.Last();
            var bookReaderToAdd      = new BookReader()
            {
                Age       = 35,
                FirstName = "Wiktor",
                LastName  = "Forst",
                Telephone = "123456789"
            };

            service.AddBookReader(bookReaderToAdd);
            int afterSize           = context.bookReaders.Count;
            var afterLastBookReader = context.bookReaders.Last();

            // check sizes
            Assert.AreNotEqual(beforeSize, afterSize);

            // check if last books aren't equal
            Assert.AreNotEqual(beforeLastBookReader, afterLastBookReader);

            // check if the book is in the list
            Assert.IsTrue(context.bookReaders.Contains(bookReaderToAdd));
        }