Make a test which fails on anisotropic systems, when neglecting head and wings correction
There are extensive corrections for anisotropic systems. However, disabling them doesn't fail the anisotropic test case P4. Namely, skipping integration over 4x4 1e-6 Monkhorst-Pack, but using a random direction (say first one in the for loop). Thus, one needs to make a test, which fails.