Xcode - 来自资产目录的单元测试 UIColor

Question

I wrote an extension for my Theme class that returns my mainColor based on my current theme. My unit tests cover theme changes but I still have problem with UIColor optional value. I can't cover the situation that UIColor could not able returns my specific color from my color catalog.

extension Theme {
var mainColor: UIColor {
    switch self {
        case .system:
          if let color = UIColor(named: "MainColor") {
             return color
          } else {
             return .clear
          }
        case .custom:
             return .yellow
      }
   }
}

I also used this line instead of unwrapping the optional but it didn't work too.

return UIColor(named: "MainColor") ?? .clear

How I unit test that the correct color is retrieved from the asset catalog?

Answer 1

The problem is that the name MainColor is hard coded, and either this color is in your asset catalog or it isn't, and you cannot control for that in a test. You need to abstract this into a method to which you can pass the color name from the test.

Answer 2

I would personally just force unwrap UIColor(named: "MainColor")! the color in my tests to assert the correct behaviour is occurring (that we are indeed able to access the desired color in the asset catalog). If we cannot access this color we will get a crash which, in a unit testing context, is actually desirable to isolate any problems.

I would also abstract the name of the color into an enum to ensure that the name is only defined in 1 place, then the possibility of naming inconsistencies between your app target and test target are removed.

enum Colors: String { 
    case main = "MainColor" 
}

Then use UIColor(named: Colors.main.rawValue) to access the color.