additional tests for mrc

- test mrc ValueError for triclinic boxes with EMD 3001
- test direct file init and read() on empty class

gridData/mrc.py

@@ -95,7 +95,7 @@ def read(self, filename):
         if filename is not None:
             self.filename = filename
         with mrcfile.open(filename) as mrc:
-            if not mrc.is_volume():
+            if not mrc.is_volume():                           #pragma: no cover
                 raise ValueError(
                     "MRC file {} is not a volumetric density.".format(filename))
             self.header = h = mrc.header.copy()

gridData/tests/datafiles/__init__.py

@@ -10,6 +10,8 @@
 # from http://www.ebi.ac.uk/pdbe/coordinates/files/1jzv.ccp4
 # (see issue #57)
 CCP4_1JZV = resource_filename(__name__, '1jzv.ccp4')
+# from https://github.com/ccpem/mrcfile/blob/master/tests/test_data/EMD-3001.map.bz2
+MRC_EMD3001 = resource_filename(__name__, 'EMD-3001.map.bz2')
 # water density around M2 TM helices of nAChR from MD simulations
 # [O. Beckstein and M. S. P. Sansom. Physical Biology 3(2):147-159, 2006]
 gOpenMol = resource_filename(__name__, 'nAChR_M2_water.plt')

gridData/tests/test_mrc.py

@@ -11,17 +11,31 @@
 from . import datafiles
 
 @pytest.fixture(scope="module")
-def g():
+def g1():
     return Grid(datafiles.CCP4, file_format="MRC")
 
-def test_ccp4(g):
+@pytest.fixture(scope="module")
+def g2():
+    data = mrc.MRC()
+    data.read(datafiles.CCP4)
+    grid, edges = data.histogramdd()
+    return Grid(grid=grid, edges=edges)
+
+def test_ccp4_Grid(g1):
+    _test_ccp4(g1)
+
+def test_ccp4_mrc(g2):
+    _test_ccp4(g2)
+
+def _test_ccp4(g):
     POINTS = 192
     assert_equal(g.grid.flat, np.arange(1, POINTS+1))
     assert_equal(g.grid.size, POINTS)
     assert_almost_equal(g.delta, [3./4, .5, 2./3])
     assert_equal(g.origin, np.zeros(3))
 
 
+
 @pytest.fixture(scope="module")
 def ccp4data():
     return mrc.MRC(datafiles.CCP4_1JZV)
@@ -76,3 +90,8 @@ def test_ccp4_read_header(ccp4data, name, value):
     else:
         assert_equal(ccp4data.header[name], value)
 
+def test_triclinic_ValueError():
+    with pytest.raises(ValueError,
+                       match="Only orthorhombic unitcells are currently "
+                       "supported, not"):
+        Grid(datafiles.MRC_EMD3001, file_format="MRC")