shortened test for monotonous increase of material index after sorting

python/tests/test_Geom.py

@@ -208,8 +208,7 @@ class TestGeom:
     def test_sort(self):
         grid = np.random.randint(5,20,3)
         m = Geom(np.random.randint(1,20,grid)*3,np.ones(3)).sort().material.flatten(order='F')
-        assert m[0] == m.min()
-        for i,v in enumerate(m[1:]):
+        for i,v in enumerate(m):
             assert v > m[:i+1].max() or v in m[:i+1]
 
     @pytest.mark.parametrize('axis_angle',[np.array([1,0,0,86.7]), np.array([0,1,0,90.4]), np.array([0,0,1,90]),