git - What is the best way to share some personal test code between repositories by CocoaPods podspec dependency? -

i have 2 repositories personal test on objective-c.(pod_a & pod_b)

there malloc functions @ repositories, create other repository put same functions.(pod_c)

then setting pod_a.podspec

s.dependency 'pod_c', :git => 'https://github.com/myname/pod_c.git' 

i pod install pod_a fail, find issues on podspec dependency. seems unsupported dependency

s.dependency :git 

how create cocoapods podspec has dependency exists outside of specs? is there way specify dependency on branch when building cocoapod?