refactor: update imports and switch to pytest for testing

tests/config/test_gaussian_config.py

@@ -0,0 +1,41 @@
+from diceplayer.config.gaussian_config import GaussianConfig
+
+import pytest
+
+
+class TestGaussianConfig:
+    def test_class_instantiation(self):
+        gaussian_dto = GaussianConfig(
+            level="test",
+            qmprog="g16",
+            keywords="test",
+        )
+
+        assert isinstance(gaussian_dto, GaussianConfig)
+
+    def test_is_valid_qmprog(self):
+        with pytest.raises(ValueError):
+            GaussianConfig(
+                level="test",
+                qmprog="test",
+                keywords="test",
+            )
+
+    def test_is_valid_level(self):
+        with pytest.raises(ValueError):
+            GaussianConfig(
+                level=None,
+                qmprog="g16",
+                keywords="test",
+            )
+
+    def test_from_dict(self):
+        gaussian_dto = GaussianConfig.model_validate(
+            {
+                "level": "test",
+                "qmprog": "g16",
+                "keywords": "test",
+            }
+        )
+
+        assert isinstance(gaussian_dto, GaussianConfig)