fix: export headers

test-helpers.xcodeproj/project.pbxproj

@@ -9,7 +9,7 @@
 /* Begin PBXBuildFile section */
 		CDD966162B654D290091D92C /* GoogleMock.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = CDD9660C2B654D1B0091D92C /* GoogleMock.framework */; };
 		CDD966182B654D490091D92C /* test_helper_test.cxx in Sources */ = {isa = PBXBuildFile; fileRef = CDD966172B654D490091D92C /* test_helper_test.cxx */; };
-		CDD966192B654DDC0091D92C /* testing in Headers */ = {isa = PBXBuildFile; fileRef = CD6031032AF6779E000D9F31 /* testing */; };
+		CDD966192B654DDC0091D92C /* testing in Headers */ = {isa = PBXBuildFile; fileRef = CD6031032AF6779E000D9F31 /* testing */; settings = {ATTRIBUTES = (Public, ); }; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */