Building: the Kladde in version 1

What you learn in this lesson

• build a feature pull request by pull request: test, model, console, check
• keep rules that involve several contacts and appointments in the model and test them there
• extend a file format so that older files still load
• build searching, choosing and confirmations in the console so that tests check them without a keyboard
• bring in holidays from an unreliable source without the Kladde getting stuck without them
• write a CSV file that a spreadsheet reads correctly