Better integration tests

The old integration tests needed to be removed for copyright reasons. We need new integration tests.

https://github.com/linkedin/opticss/commit/ac97a0fabd4c05be3b34c75fba804c14e22e5cd8

Start by reviewing commit ac97a0fabd4c05be3b34c75fba804c14e22e5cd8 and the repository's current test setup to understand what integration coverage was removed. Identify the expected integration scenarios from the surrounding project behavior, then add replacement tests using original, non-copyrighted cases. Done means the new integration tests run successfully and restore meaningful coverage without the removed material.

Written by the indexing model from the issue text.