Move all unit tests to the Tests/Unit folder

GoogleDataLogger.podspec

@@ -35,7 +35,7 @@ Shared library for iOS SDK data logging needs.
   }
 
   # Test specs
-  s.test_spec 'Tests' do |test_spec|
-    test_spec.source_files = 'GoogleDataLogger/Tests/**/*.{h,m}'
+  s.test_spec 'UnitTests' do |test_spec|
+    test_spec.source_files = 'GoogleDataLogger/Tests/Unit/**/*.{h,m}'
   end
 end

GoogleDataLogger/Tests/GDLLogStorageTest.m → GoogleDataLogger/Tests/Unit/GDLLogStorageTest.m

@@ -42,6 +42,7 @@ @interface GDLLogStorageTest : GDLTestCase
 /** The test prioritizer implementation. */
 @property(nullable, nonatomic) GDLTestPrioritizer *testPrioritizer;
 
+/** The uploader fake. */
 @property(nonatomic) GDLUploaderFake *uploaderFake;
 
 @end