Defensive Coding for Safe Migrations

You may have discovered that programming is hard!

In my experience Test driven development makes it easier, and we should definitely listen if the code is trying to tell us that it doesn’t want to do a thing, but there are some times when we just have to push on through difficulties to get out the other side.

This week’s task should have been easy - just writing a composite version of our items repository. In practice it was hampered by finding a bug in our database mapping, having to deal with JSON mapping issues, and my insistence that we shouldn’t risk breaking a working system.

At least this last requirement means that we can explore defensive coding.

In the middle of this episode I find a bug that is miraculously fixed through the power of video editing. The full diagnosis, testing and fixing is the subject of the previous episode - https://youtu.be/vuMN0IU4EVg

This is part 74 of an exploration of where a Test Driven Development implementation of the Gilded Rose stock control system might take us in Kotlin. You can see the whole series as a playlist
https://www.youtube.com/playlist?list=PL1ssMPpyqociJNwykAOB9_KEZVW7BW7m2
and the code on GitHub
https://github.com/dmcg/gilded-rose-tdd

Other database-specific episodes are collected in a playlist https://www.youtube.com/playlist?list=PL1ssMPpyqoci7HFHOmNbzkT_OAVqr9JBu

If you like this, you’ll probably like my book Java to Kotlin, A Refactoring Guidebook
(http://java-to-kotlin.dev). It's about far more than just the syntax differences between the languages - it shows how to upgrade your thinking to a more functional style.

I have some free time between producing videos and working for team Gilded Rose. If you like these videos I'd like to work with you - please get in touch - [email protected]