[brief] Update the tests for the CuDNN context.

[detailed]
- Ensure that it works regardless of the initial value assigned.

test/test_core.py

@@ -101,14 +101,18 @@ def test_functions(self) -> None:
             with pytest.raises(RuntimeError):
                 cuda.requires_cuda_support()
 
+    def _check_cudnn(self, val: bool) -> None:
+        torch.backends.cudnn.benchmark = val
+        assert torch.backends.cudnn.benchmark == val
+        with cuda.DisableCuDNNBenchmarkContext():
+            assert not torch.backends.cudnn.benchmark
+
+        assert torch.backends.cudnn.benchmark == val
+
     def test_disable_cudnn_context(self) -> None:
         if torch.cuda.is_available():
-            torch.backends.cudnn.benchmark = True
-
-            assert torch.backends.cudnn.benchmark
-            with cuda.DisableCuDNNBenchmarkContext():
-                assert not torch.backends.cudnn.benchmark
-            assert torch.backends.cudnn.benchmark
+            self._check_cudnn(True)
+            self._check_cudnn(False)
 
 
 @dataclasses.dataclass