Adding improper rotations to tests

meta.yaml

@@ -1,6 +1,6 @@
 package:
   name: "sphecerix"
-  version: "0.3.0"
+  version: "0.4.0"
 
 source:
   path: .

sphecerix/_version.py

@@ -1 +1 @@
-__version__ = "0.3.0"
+__version__ = "0.4.0"

tests/test_improper_rotation.py

@@ -0,0 +1,38 @@
+import unittest
+import numpy as np
+import sys
+import os
+from scipy.spatial.transform import Rotation as R
+
+# add a reference to load the Sphecerix library
+sys.path.append(os.path.join(os.path.dirname(__file__), '..'))
+
+# import functions
+from sphecerix import tesseral_wigner_D_improper
+
+class TestImproperRotation(unittest.TestCase):
+    """
+    Test improper rotation matrices
+    """
+
+    def test_improper_s4(self):
+        """
+        Test the result under an improper rotation
+        """
+        # construct rotation vector
+        axis = np.array([1,0,0])
+        Robj = R.from_rotvec(axis * np.pi / 2)
+
+        # construct wigner D matrix
+        D = tesseral_wigner_D_improper(1, Robj)
+
+        # assert that determinant is -1
+        np.testing.assert_almost_equal(np.linalg.det(D), -1)
+
+        # rotate a point at +x,+y,+z under S4 to -x,-y,+z
+        # note that the ordering in the vector (using increasing value of m)
+        # is [y,z,x]
+        np.testing.assert_almost_equal(D @ np.array([1,1,1]), np.array([-1,1,-1]))
+
+if __name__ == '__main__':
+    unittest.main()