add domain extra kwarg test

tests/unit/domain/test_domain.py

@@ -0,0 +1,16 @@
+import pytest
+
+from rubicon_ml.domain.project import Project
+
+
+@pytest.mark.parametrize(
+    ["domain_cls", "required_kwargs"],
+    [(Project, {"name": "test_domain_extra_kwargs"})],
+)
+def test_domain_extra_kwargs(domain_cls, required_kwargs):
+    domain = domain_cls(extra="extra", **required_kwargs)
+
+    assert "extra" not in domain.__dict__
+
+    for key, value in required_kwargs.items():
+        assert getattr(domain, key) == value