Set `SWIFT_VERSION` to test native targets during validation

CHANGELOG.md

@@ -18,6 +18,10 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
 
 ##### Bug Fixes
 
+* Set `SWIFT_VERSION` to test native targets during validation  
+  [Dimitris Koutsogiorgas](https://github.com/dnkoutso)
+  [#7216](https://github.com/CocoaPods/CocoaPods/pull/7216)
+
 * Add copied resources' paths to "Copy Pods Resources" output file list  
   [igor-makarov](https://github.com/igor-makarov)
   [#6936](https://github.com/CocoaPods/CocoaPods/issues/6936)

lib/cocoapods/validator.rb

@@ -478,6 +478,13 @@ module Pod
             (build_configuration.build_settings['OTHER_CFLAGS'] ||= '$(inherited)') << ' -Wincomplete-umbrella'
             build_configuration.build_settings['SWIFT_VERSION'] = swift_version if pod_target.uses_swift?
           end
+          if pod_target.uses_swift?
+            pod_target.test_native_targets.each do |test_native_target|
+              test_native_target.build_configuration_list.build_configurations.each do |build_configuration|
+                build_configuration.build_settings['SWIFT_VERSION'] = swift_version
+              end
+            end
+          end
         end
         if target.pod_targets.any?(&:uses_swift?) && consumer.platform_name == :ios &&
             (deployment_target.nil? || Version.new(deployment_target).major < 8)