@U3Y18N0UC do you then have to modify your source code to point to the right env var each time you switch between running tests or running a local/dev environment?

Not really, you just have to inject dependencies. For example, instead of defining a "global db pool" you can create a "generate-pool" function that will receive the arguments and return a db pool. In your main app, you just use (let [db-conn (generate-pool <db-env>)] (start-the-app! db-conn))

And in your test file, you do the (let [db-conn (generate-pool <test-db-env>)] (start-the-app! db-conn))

great, thanks for those suggestions:) For my current code base it was easiest to use jvm-opts in my :test alias per @U04V70XH6’s suggestion, but I’ll play around with your solution too. Always good to learn multiple ways of doing things