diff --git a/mlos_core/mlos_core/tests/optimizers/one_hot_test.py b/mlos_core/mlos_core/tests/optimizers/one_hot_test.py
index 0c36859b68..46d549ae54 100644
--- a/mlos_core/mlos_core/tests/optimizers/one_hot_test.py
+++ b/mlos_core/mlos_core/tests/optimizers/one_hot_test.py
@@ -13,7 +13,7 @@
 import numpy.typing as npt
 import ConfigSpace as CS
 
-from mlos_core.optimizers import SmacOptimizer
+from mlos_core.optimizers import BaseOptimizer, SmacOptimizer
 
 # pylint: disable=protected-access,redefined-outer-name
 
@@ -68,79 +68,86 @@ def one_hot_series() -> npt.NDArray:
     ])
 
 
-def test_to_1hot_data_frame(configuration_space: CS.ConfigurationSpace,
-                            data_frame: pd.DataFrame, one_hot_data_frame: npt.NDArray) -> None:
+@pytest.fixture
+def optimizer(configuration_space: CS.ConfigurationSpace) -> BaseOptimizer:
+    """
+    Test fixture for the optimizer. Use it to test one-hot encoding/decoding.
+    """
+    return SmacOptimizer(
+        parameter_space=configuration_space,
+    )
+
+
+def test_to_1hot_data_frame(optimizer: BaseOptimizer,
+                            data_frame: pd.DataFrame,
+                            one_hot_data_frame: npt.NDArray) -> None:
     """
     Toy problem to test one-hot encoding of dataframe.
     """
-    optimizer = SmacOptimizer(parameter_space=configuration_space)
     assert optimizer._to_1hot(data_frame) == pytest.approx(one_hot_data_frame)
 
 
-def test_to_1hot_series(configuration_space: CS.ConfigurationSpace,
+def test_to_1hot_series(optimizer: BaseOptimizer,
                         series: pd.Series, one_hot_series: npt.NDArray) -> None:
     """
     Toy problem to test one-hot encoding of series.
     """
-    optimizer = SmacOptimizer(parameter_space=configuration_space)
     assert optimizer._to_1hot(series) == pytest.approx(one_hot_series)
 
 
-def test_from_1hot_data_frame(configuration_space: CS.ConfigurationSpace,
-                              data_frame: pd.DataFrame, one_hot_data_frame: npt.NDArray) -> None:
+def test_from_1hot_data_frame(optimizer: BaseOptimizer,
+                              data_frame: pd.DataFrame,
+                              one_hot_data_frame: npt.NDArray) -> None:
     """
     Toy problem to test one-hot decoding of dataframe.
     """
-    optimizer = SmacOptimizer(parameter_space=configuration_space)
     assert optimizer._from_1hot(one_hot_data_frame).to_dict() == data_frame.to_dict()
 
 
-def test_from_1hot_series(configuration_space: CS.ConfigurationSpace,
-                          series: pd.Series, one_hot_series: npt.NDArray) -> None:
+def test_from_1hot_series(optimizer: BaseOptimizer,
+                          series: pd.Series,
+                          one_hot_series: npt.NDArray) -> None:
     """
     Toy problem to test one-hot decoding of series.
     """
-    optimizer = SmacOptimizer(parameter_space=configuration_space)
     one_hot_df = optimizer._from_1hot(one_hot_series)
     assert one_hot_df.shape[0] == 1, f"Unexpected number of rows ({one_hot_df.shape[0]} != 1)"
     assert one_hot_df.iloc[0].to_dict() == series.to_dict()
 
 
-def test_round_trip_data_frame(configuration_space: CS.ConfigurationSpace, data_frame: pd.DataFrame) -> None:
+def test_round_trip_data_frame(optimizer: BaseOptimizer, data_frame: pd.DataFrame) -> None:
     """
     Round-trip test for one-hot-encoding and then decoding a data frame.
     """
-    optimizer = SmacOptimizer(parameter_space=configuration_space)
     df_round_trip = optimizer._from_1hot(optimizer._to_1hot(data_frame))
     assert df_round_trip.x.to_numpy() == pytest.approx(data_frame.x)
     assert (df_round_trip.y == data_frame.y).all()
     assert (df_round_trip.z == data_frame.z).all()
 
 
-def test_round_trip_series(configuration_space: CS.ConfigurationSpace, series: pd.DataFrame) -> None:
+def test_round_trip_series(optimizer: BaseOptimizer, series: pd.DataFrame) -> None:
     """
     Round-trip test for one-hot-encoding and then decoding a series.
     """
-    optimizer = SmacOptimizer(parameter_space=configuration_space)
     series_round_trip = optimizer._from_1hot(optimizer._to_1hot(series))
     assert series_round_trip.x.to_numpy() == pytest.approx(series.x)
     assert (series_round_trip.y == series.y).all()
     assert (series_round_trip.z == series.z).all()
 
 
-def test_round_trip_reverse_data_frame(configuration_space: CS.ConfigurationSpace, one_hot_data_frame: npt.NDArray) -> None:
+def test_round_trip_reverse_data_frame(optimizer: BaseOptimizer,
+                                       one_hot_data_frame: npt.NDArray) -> None:
     """
     Round-trip test for one-hot-decoding and then encoding of a numpy array.
     """
-    optimizer = SmacOptimizer(parameter_space=configuration_space)
     round_trip = optimizer._to_1hot(optimizer._from_1hot(one_hot_data_frame))
     assert round_trip == pytest.approx(one_hot_data_frame)
 
 
-def test_round_trip_reverse_series(configuration_space: CS.ConfigurationSpace, one_hot_series: npt.NDArray) -> None:
+def test_round_trip_reverse_series(optimizer: BaseOptimizer,
+                                   one_hot_series: npt.NDArray) -> None:
     """
     Round-trip test for one-hot-decoding and then encoding of a numpy array.
     """
-    optimizer = SmacOptimizer(parameter_space=configuration_space)
     round_trip = optimizer._to_1hot(optimizer._from_1hot(one_hot_series))
     assert round_trip == pytest.approx(one_hot_series)