當在主APP和unit test的target中都需要使用到某一個庫，且這時使用pod進行配置時，如果給兩個target都配置了改庫，就會有一個Class is implemented in both warning when running unit tests 的警告：

形式如下：

Class AFQueryStringPair is implemented in both
/XXX/DuplicateClassImplementation.app/DuplicateClassImplementation and
/XXX/DuplicateClassImplementationTests.xctest/DuplicateClassImplementationTests.
One of the two will be used. Which one is undefined.

可以修改Podfile避免此問題，主要是讓單元測試的target繼承主app的search path：

target 'App' do
    pod 'GoogleAnalytics' , '~> 3.0'
    pod 'GoogleTagManager' , '~> 3.0'

     pod 'SDWebImage', '~>3.7'
     platform :ios, '8.0'
     use_frameworks!

     target 'App Unit Tests' do
         inherit! :search_paths
     end
 end

 target 'App Enterprise' do
     pod 'GoogleAnalytics' , '~> 3.0'
     pod 'GoogleTagManager' , '~> 3.0'

     pod 'SDWebImage', '~>3.7'
     platform :ios, '8.0'
     use_frameworks!
 end