Introduce subjectKwargs method

Author: Maxcode123

src/unittest_extensions/case.py

@@ -1,7 +1,8 @@
 from unittest import TestCase as BaseTestCase
-from typing import Any
+from typing import Any, Dict
 from abc import abstractmethod
 from warnings import warn
+from copy import deepcopy
 
 from unittest_extensions.error import TestError
 
@@ -37,6 +38,18 @@ def test_int_plus_float(self):
     @abstractmethod
     def subject(self, **kwargs) -> Any: ...
 
+    def subjectKwargs(self) -> Dict[str, Any]:
+        """
+        Return the keyword arguments of the subject.
+
+        The dictionary returned is a copy of the original arguments. Thus,
+        the arguments that the subject receives cannot be mutated by mutating
+        the returned object of this method.
+        """
+        # NOTE: deepcopy keeps a reference of the copied object. This can cause
+        # issues with memory.
+        return deepcopy(self._subjectKwargs)
+
     def result(self) -> Any:
         """
         Result of the `subject` called with arguments defined by the `args`

src/unittest_extensions/tests/test_use_case.py

@@ -153,3 +153,32 @@ def test_manually_change_state_cached_result(self):
         self.assertEqual(self.cachedResult(), 2)
         self.instance.state_var += 1
         self.assertEqual(self.cachedResult(), 2)
+
+
+class TestSubjectKwargs(TestCase):
+    def subject(self, a, b):
+        return a + b
+
+    @args({"a": 1, "b": 2})
+    def test_kwarg_values(self):
+        self.assertDictEqual(self.subjectKwargs(), {"a": 1, "b": 2})
+
+    @args({"a": 3, "b": 4})
+    def test_different_kwarg_values(self):
+        self.assertDictEqual(self.subjectKwargs(), {"a": 3, "b": 4})
+
+    @args({"a": 1, "b": 2})
+    def test_kwargs_are_not_mutated(self):
+        self.subjectKwargs()["b"] = None
+        self.assertDictEqual(self._subjectKwargs, {"a": 1, "b": 2})
+        self.assertDictEqual(self.subjectKwargs(), {"a": 1, "b": 2})
+
+
+class TestSubjectMutableKwargs(TestCase):
+    def subject(self, lst):
+        return lst
+
+    @args({"lst": [1, 2]})
+    def test_mutable_kwargs(self):
+        self.subjectKwargs()["lst"].append(3)
+        self.assertDictEqual(self._subjectKwargs, {"lst": [1, 2]})