When I was at Mozilla we used a number of different strategies (including having content pre-translated before the design process started).

A fast-and-dirty test we'd use was this bookmarklet cheekily called "dasFauxGermanhausen" that turned all of the text on the page into, well, faux German.

This obviously is only useful for web-based designs, but if it's helpful to anyone I posted the bookmarklet here - please keep in mind this is like eight years old, but it still works.

Scroll, baby, scroll.