Peter Marklund

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Testing Rails Migrations

Is it worthwhile testing Rails ActiveRecord migrations? After all, they are only intended to be run once so regression testing isn't an issue. I honestly haven't tested my migrations much in the past but I recently decided to give it a try. I was surprised by the fact that it wasn't very different from testing any other part of my application. My test didn't end up having very good coverage so I still needed to test the migration manually. As usual when writing tests, I found that it drove a series of extract method refactorings. I went from having all code in the up method to having five shorter methods. A different approach to migration testing is to add sanity checks at the end of migrations that output an error message in production if the outcome of the migration wasn't what was expected.