public void CommandCompositeBase_Add_ReturnThis()
    {
        // Arrange
        var command = new Command();

        // Act
        var commandComposite = new CommandComposite();
        var actual           = commandComposite.Add(command);

        //Assert
        Assert.AreEqual(actual, commandComposite);
    }
    public void CommandCompositeBase_Add_Exception()
    {
        // Arrange
        var actual = false;

        // Act
        var compositeCommand = new CommandComposite();

        try
        {
            compositeCommand.Add(null);
        }
        catch (ArgumentNullException)
        {
            actual = true;
        }

        //Assert
        Assert.IsTrue(actual);
    }