More tests for CG, but no changes in the code

tests/test_cg.py

@@ -20,9 +20,7 @@
     # j1 = 1, j2 = 1/2
     ((2, 2, 4, 2, 0, 2), np.sqrt(1.0 / 2)),
 )
-
-
-def test_wigner3j_value():
+def test_clebsch_gordan_value():
     # scalar test
     for three_j, expected in CG:
         print(three_j)
@@ -34,3 +32,23 @@ def test_wigner3j_value():
     expected = np.array([value for _, value in CG]).T
     actual = clebsch_gordan(*three_j)
     assert np.allclose(actual, expected)
+
+
+# reference from https://en.wikipedia.org/wiki/Clebsch%E2%80%93Gordan_coefficients#Special%20cases
+def test_clebsch_gordan_value_more():
+    # if J3 = M3 = 0
+    for offset in [0, 0.5]:
+        for j1 in np.arange(offset, 4 + offset):
+            for j2 in np.arange(offset, 3 + offset):
+                m1 = np.arange(-j1, j1 + 1)[:, np.newaxis]
+                m2 = np.arange(-j2, j2 + 1)
+                expected = np.where(
+                    (j1 == j2) * (m1 == -m2), 
+                    (-1) ** (j1 - m1) / np.sqrt(2 * j1 + 1),
+                    0.0
+                )
+                actual = clebsch_gordan(
+                    int(2 * j1), int(2 * j2), 0, (2 * m1).astype(int), (2 * m2).astype(int), 0
+                )
+                assert np.allclose(expected, actual)
+