I am pretty sure you can run most code in your build.boot file, but I haven't used boot for a while. Do you know what test runner you are using? I would activate those asserts before you run the tests. I would put them anywhere you can inject code before test code is run, which varies based on how you run the tests. I am using circleci.test (https://github.com/circleci/circleci.test) with Leiningen to run tests and circleci.test has a global fixture that can run code before and after any tests are run. In my code I would probably activate the asserts in that fixture.

In boot you may just be able to add it to your test task at the top of the task definition

If you use a test task from another library, then you may be able to add a test task to your own built.boot file, activate your assertions and then call the actual test task from that other library