diff --git a/tests/ert/unit_tests/test_libres_facade.py b/tests/ert/unit_tests/test_libres_facade.py
index be24bc0d8ae..55155765221 100644
--- a/tests/ert/unit_tests/test_libres_facade.py
+++ b/tests/ert/unit_tests/test_libres_facade.py
@@ -2,12 +2,15 @@
 from datetime import datetime, timedelta
 from textwrap import dedent
 
+import numpy as np
 import pytest
+from pandas import ExcelWriter
 from pandas.core.frame import DataFrame
 from resdata.summary import Summary
 
 from ert.config import ErtConfig
-from ert.enkf_main import sample_prior
+from ert.config.design_matrix import DESIGN_MATRIX_GROUP, DesignMatrix
+from ert.enkf_main import sample_prior, save_design_matrix_to_ensemble
 from ert.libres_facade import LibresFacade
 from ert.storage import open_storage
 
@@ -241,3 +244,53 @@ def test_load_gen_kw_not_sorted(storage, tmpdir, snapshot):
 
         data = ensemble.load_all_gen_kw_data()
         snapshot.assert_match(data.round(12).to_csv(), "gen_kw_unsorted")
+
+
+@pytest.mark.parametrize(
+    "reals, expect_error",
+    [
+        pytest.param(
+            list(range(10)),
+            False,
+            id="correct_active_realizations",
+        ),
+        pytest.param([10, 11], True, id="incorrect_active_realizations"),
+    ],
+)
+def test_save_parameters_to_storage_from_design_dataframe(
+    tmp_path, reals, expect_error
+):
+    design_path = tmp_path / "design_matrix.xlsx"
+    ensemble_size = 10
+    a_values = np.random.default_rng().uniform(-5, 5, 10)
+    b_values = np.random.default_rng().uniform(-5, 5, 10)
+    c_values = np.random.default_rng().uniform(-5, 5, 10)
+    design_matrix_df = DataFrame({"a": a_values, "b": b_values, "c": c_values})
+    with ExcelWriter(design_path) as xl_write:
+        design_matrix_df.to_excel(xl_write, index=False, sheet_name="DesignSheet01")
+        DataFrame().to_excel(
+            xl_write, index=False, sheet_name="DefaultValues", header=False
+        )
+    design_matrix = DesignMatrix(design_path, "DesignSheet01", "DefaultValues")
+    design_matrix.read_design_matrix()
+    with open_storage(tmp_path / "storage", mode="w") as storage:
+        experiment_id = storage.create_experiment(
+            parameters=[design_matrix.parameter_configuration[DESIGN_MATRIX_GROUP]]
+        )
+        ensemble = storage.create_ensemble(
+            experiment_id, name="default", ensemble_size=ensemble_size
+        )
+        if expect_error:
+            with pytest.raises(KeyError):
+                save_design_matrix_to_ensemble(
+                    design_matrix.design_matrix_df, ensemble, reals
+                )
+        else:
+            save_design_matrix_to_ensemble(
+                design_matrix.design_matrix_df, ensemble, reals
+            )
+            params = ensemble.load_parameters(DESIGN_MATRIX_GROUP)["values"]
+            all(params.names.values == ["a", "b", "c"])
+            np.testing.assert_array_almost_equal(params[:, 0], a_values)
+            np.testing.assert_array_almost_equal(params[:, 1], b_values)
+            np.testing.assert_array_almost_equal(params[:, 2], c_values)