After experience with several junior developers I plan to do the following to train the next one. First, let them solve an isolated problem in our code base. At

After experience with several junior developers I plan to do the following to train the next one. First, let them solve an isolated problem in our code base. At pull request step comment excessively (this is what inevitably happens with all junior developers, the PR is so huge that GitHub chokes on it). Finally, pair them with a senior developer to solve the issues raised in the PR, rather than letting them fix them alone and engage in an endless loop of commits and comments.