public void TestMicrowaveOven_WriteMessageMethod()
        {
            Mock <IWriter>     writer = new Mock <IWriter>();
            Mock <IRepository> repo   = new Mock <IRepository>();

            IClient microwave = new MicrowaveOven(writer.Object, repo.Object);

            microwave.WriteMessage(Msg);

            writer.Verify(w => w.WriteLine(It.Is <string>(s => s == Msg)), Times.Once, "Message hasn't been sent!");
        }