And that is: remember to remove import tables in your Setup pages.
The way DoFixtures work, is that they put the test into a ‘flow’ mode. However, that works only if the DoFixture is the first table in the page. Even the harmless import table should be removed. Which is not a big deal, since you normally have few additional fixtures in the page. However, it also means that you cannot use a Setup page with an import table to define default packages.
One thing I don’t like about FitLibrary, is that it does not have its own website (or rather, it used to, on SourceForge, but all pages have been removed), so you lack a reference documentation. What you end up doing, is using the FitLibrary that comes with Fitnesse, only to realize that many comments on the Internet refer to a more recent version. And you have to download the latest version of Fitlibrary (an its documentation)Â anyway.