Judge by API

I think the best way to judge about the quality of a developer is to look at the API he has designed. If he really thinks about his code he designs the API with extreme care (here the C++ variant):

• clean formatting


• concise naming of methods


• no redundant methods, if necessary provide default parameters instead of multiple similar methods


• implementation specifics like headers of third-party libs don't shine through


• only few public methods


• and even fewer virtual methods


• short parameter lists; instead of long parameter lists use parameter objects with senseful default values


• comments on dependencies


• thorough documentation, embedded code samples

I could go on and on. Such classes can be used like a breeze.