public void AreasOfWindowsEqualsAreaOfDesktop()
{
// ARRANGE
var input = mock.CreateWindows(resolution);
var output = Helper.DeepCopy(input);
// ACT
sut.Calculate(output);
// ASSERT
Assert.NotNull(output);
var areaOfWindows = output
.Select(window => window.Area())
.Sum();
var areaOfDesktop = sut.ScreenHeight * sut.ScreenWidth;
Assert.AreEqual(areaOfDesktop, areaOfWindows);
}