Added note explaining why the WordCloudViewModel singleton's OptionsViewModel property must have its FontFamilyOptions property (i.e. wordCloudViewModel.OptionsViewModel.FontFamilyOptions) assigned to (with StaticHelpers.EnumerateInstalledFonts() in the startup object's code-behind file. The reason for this is that, by calling EnumerateInstalledFonts(), Fonts.Typefaces is used, the reference of which seems to occur on the UI thread. If this method is called either in the constructor of the WordCloudViewModel or the OptionsViewModel, any test involving either ViewModel (e.g. nearly all the logic in the entire application) will automatically fail due to an UnauthorizedAccessException.