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The Mikado Method
The Mikado Method can help you find the troubling dependencies any large refactoring is affected by. You build the Mikado graph using the naïve approach from your goal and out. By drawing the graph, you ensure that those dependencies are remembered and communicated to fellow workers or the future you, like a memento. By working the Mikado graph from the leaves in, you can perform big changes while keeping the system in a deliverable state, all the time.