Maybe you've already tried it too often (you only have three attempts)?

The :test out of this skill" option recently moved up to the top of the page and is now part of section that tracks your progress.

Thanks for your answers. @floscher I 'tested out' of level 7, to level 8. Now I'm on level 9 but the 'test out' thing has not come back. @dybbuk - no it's not there!

I strongly recommend going through the lengthy process of doing the exercises, unless you are certain of testing out of a skill without them. Not only do they offer revision, the computer generated sentences/phrases are often not natural, as are their translations.