Integration test are a compromise. e2e tests may be quite expensive to run (for a web application, you might need to run your backend and a web browser, possibly in a docker container - and the whole thing will also run slower). Efficiency matters a lot.

You can have robust testing by combining the two. You can check that the whole thing runs end to end once, and then test all the little features / variations using integration tests.

That's what we do for XWiki.

https://dev.xwiki.org/xwiki/bin/view/Community/Testing/#HTes...