improve test coverage

tests/unit_tests/attributes/test_impl_attribute_registry.py

@@ -0,0 +1,34 @@
+""" checks the attribute registry logic mapping attribute names to classes implementing them
+ and handling different variants of these implementations picked depending on the choice of
+ dynamics and formulae options """
+
+import pytest
+
+from PySDM.attributes import Multiplicity
+from PySDM.attributes.impl import get_attribute_class, register_attribute
+
+
+class TestAttributeRegistry:
+    """groups multiple tests to facilitate execution"""
+
+    @staticmethod
+    def test_get_attribute_class_ok():
+        """checks if inquiring for a valid attribute name yields a valid class"""
+        assert get_attribute_class("multiplicity") is Multiplicity
+
+    @staticmethod
+    def test_get_attribute_class_fail():
+        """checks if inquiring for an invalid attribute name raises an exception"""
+        with pytest.raises(ValueError):
+            assert get_attribute_class("lorem ipsum")
+
+    @staticmethod
+    def test_get_attribute_class_variant_fail():
+        """checks if variant logic properly throws an exception if no variant match found"""
+
+        @register_attribute(name="umaminess", variant=lambda _, __: False)
+        class Umaminess:  # pylint: disable=unused-variable,too-few-public-methods
+            """Dummy class"""
+
+        with pytest.raises(AssertionError):
+            assert get_attribute_class("umaminess")