TST: Additional tests for getting slice normal from DicomWrapper

Make sure the sign from the CSA slice norm is used.
Test assertion that CSA slice norm and cross product are parallel.

Author: moloney

nibabel/nicom/tests/test_dicomwrappers.py

@@ -144,13 +144,30 @@ def test_slice_indicator():
     dw_empty = didw.Wrapper()
     assert_true(dw_empty.slice_indicator is None)
 
+
 @dicom_test
-def test_slice_normal():
-    dw = didw.wrapper_from_file(DATA_FILE_SLC_NORM)
-    
+def test_orthogonal():
     #Test that the slice normal is sufficiently orthogonal
+    dw = didw.wrapper_from_file(DATA_FILE_SLC_NORM)
     R = dw.rotation_matrix
     assert  np.allclose(np.eye(3),
                         np.dot(R, R.T),
                         atol=1e-6)
-    
+                    
+@dicom_test
+def test_use_csa_sign():
+    #Test that we get the same slice normal, even after swapping the iop 
+    #directions
+    dw = didw.wrapper_from_file(DATA_FILE_SLC_NORM)
+    iop = dw.image_orient_patient
+    dw.image_orient_patient = np.c_[iop[:,1], iop[:,0]]
+    dw2 = didw.wrapper_from_file(DATA_FILE_SLC_NORM)
+    assert np.allclose(dw.slice_normal, dw2.slice_normal)
+
+@dicom_test
+def test_assert_parallel():
+    #Test that we get an AssertionError if the cross product and the CSA 
+    #slice normal are not parallel
+    dw = didw.wrapper_from_file(DATA_FILE_SLC_NORM)
+    dw.image_orient_patient = np.c_[[1., 0., 0.], [0., 1., 0.]]
+    assert_raises(AssertionError, dw.__getattribute__, 'slice_normal')