add test for inverted colors identifier

Author: kruegermj

Example/SnapshotTests/InvertColorsTests.swift

@@ -25,7 +25,19 @@ final class InvertColorsTests: SnapshotTestCase {
         let viewController = InvertColorsViewController()
         viewController.view.frame = UIScreen.main.bounds
 
+        FBSnapshotVerifyView(viewController.view, identifier: "disabled")
+
         SnapshotVerifyWithInvertedColors(viewController.view)
+
+        // Run the plain snapshot a second time to ensure that the view was restored to its original state.
+        FBSnapshotVerifyView(viewController.view, identifier: "disabled")
+    }
+
+    func testInvertColorsWithIdentifier() {
+        let viewController = InvertColorsViewController()
+        viewController.view.frame = UIScreen.main.bounds
+
+        SnapshotVerifyWithInvertedColors(viewController.view, identifier: "someIdentifier")
     }
 
 }