I have faced with the same issue and after lot of googling and asking on the CocoaPods github I have finally found the suitable answer.
It’s not possible to set a local pod as a dependency, but it’s possible to set a pod’s source for a specific Podfile, which will work the same way.
E.g., in your podspec, you still have ()
s.dependency = 'my pod', '~> 1.0' # or whatever version you have
Then in your Example/demo/test project’s Podfile:
pod 'my pod', :path => '/path/to/the/local/my_pod'
Then just run pod install and you will see both pods as a Development pods.
This way is very useful when you’re developing 2 pods (one of which is dependend on the other) simultaneously, yet for release you will still have to publish your pod to the repo (either CocoaPods or a private repo).