In my UI test I'm trying to force the app's appearance (light or dark). When the system appearance is light, I can force the app to be dark with this code:
var app = XCUIApplication()
app.launchArguments += ["-AppleInterfaceStyle", "Dark"]
app.launch()
But replacing Dark with Light doesn't have any effect: if the system appearance is dark: the app remains dark. Is this not possible?