Made atomtypeTest unit tests simpler to read and edit.
Made atomtypeTest unit tests simpler to read and edit.

This commit doesn't change what they do, just refactors the code a bit.
enochd/RMG-Py,nyee/RMG-Py,KEHANG/RMG-Py,pierrelb/RMG-Py,chatelak/RMG-Py,enochd/RMG-Py,chatelak/RMG-Py,nickvandewiele/RMG-Py,nyee/RMG-Py,KEHANG/RMG-Py,comocheng/RMG-Py,faribas/RMG-Py,comocheng/RMG-Py,pierrelb/RMG-Py,faribas/RMG-Py,nickvandewiele/RMG-Py