Remove compiler errors in tests for the scenario of running tests via SPM

Author: nerdsupremacist

Tests/Mac/Helpers/NSImage+ExtensionsTests.swift

@@ -1,3 +1,4 @@
+#if os(macOS)
 import Cocoa
 @testable import Cache
 
@@ -14,3 +15,4 @@ extension NSImage {
       .representation(using: imageFileType, properties: [:])!
   }
 }
+#endif

Tests/Mac/Helpers/TestHelper+OSX.swift

@@ -1,3 +1,4 @@
+#if os(macOS)
 import Cocoa
 
 extension TestHelper {
@@ -9,3 +10,4 @@ extension TestHelper {
     return image
   }
 }
+#endif

Tests/Shared/TestHelper.swift

@@ -19,7 +19,7 @@ struct TestHelper {
     #elseif os(tvOS)
     NotificationCenter.default.post(name: UIApplication.didEnterBackgroundNotification, object: nil)
     NotificationCenter.default.post(name: UIApplication.willTerminateNotification, object: nil)
-    #else
+    #elseif os(macOS)
     NotificationCenter.default.post(name: NSApplication.willTerminateNotification, object: nil)
     NotificationCenter.default.post(name: NSApplication.didResignActiveNotification, object: nil)
     #endif

Tests/iOS/Helpers/TestHelper+iOS.swift

@@ -1,3 +1,4 @@
+#if os(iOS) || os(tvOS)
 import UIKit
 
 extension TestHelper {
@@ -14,3 +15,4 @@ extension TestHelper {
     return image!
   }
 }
+#endif

Tests/iOS/Helpers/UIImage+ExtensionsTests.swift

@@ -1,3 +1,4 @@
+#if os(iOS) || os(tvOS)
 import UIKit
 
 extension UIImage {
@@ -24,3 +25,4 @@ extension UIImage {
     return drawnImage!.cgImage!.dataProvider!.data! as Data
   }
 }
+#endif