Adding Python init file.

tests/unit_tests/cad/__init__.py

@@ -0,0 +1,9 @@
+import numpy as np
+import pytest
+
+
+def assert_unbounded(obj):
+    """Assert that a region/cell is unbounded."""
+    ll, ur = obj.bounding_box
+    assert ll == pytest.approx((-np.inf, -np.inf, -np.inf))
+    assert ur == pytest.approx((np.inf, np.inf, np.inf))

tests/unit_tests/cad/test_cad.py

@@ -1,8 +1,6 @@
 
-import pytest
-
 from subprocess import call
 
 def test_cad():
-    assert not call(["openmc"])
+    assert not call(['openmc'])