Atheism doesn't have a prescribed worldview - it is simply not believing the existence of deities.
In rational skepticism, we base our outlook on the world on four basal assumptions:
1. Reality is real.
2. Nature behaves consistently (as far as we have ascertained it).
3. Humans have the capability of understanding nature and reality.
4. The scientific method is the best framework to ascertain knowledge about nature and reality.
If any of these could be demonstrably proven false, our worldview would be shattered and we would have to go back to the drawing board and question everything we think we know.
I would also make the case that other worldviews - both religious and non-religious - use these same four basal assumptions (though they may add others).