Make egg test use new storage

tests/everest/test_egg_simulation.py

@@ -1,6 +1,8 @@
+import io
 import json
 import os
 
+import polars
 import pytest
 
 from ert.config import ErtConfig, QueueSystem
@@ -804,6 +806,27 @@ def sweetcallbackofmine(self, *args, **kwargs):
 
     assert cbtracker.called
 
+    best_batch = [b for b in run_model.ever_storage.data.batches if b.is_improvement][
+        -1
+    ]
+
+    def _df_to_string(df: polars.DataFrame):
+        strbuf = io.StringIO()
+        schema = df.schema
+        df.with_columns(
+            polars.col(c) for c in df.columns if schema[c] == polars.Float32
+        ).write_csv(strbuf)
+
+        return strbuf.getvalue()
+
+    best_objectives_csv = _df_to_string(best_batch.perturbation_objectives)
+    best_objective_gradients_csv = _df_to_string(best_batch.batch_objective_gradient)
+    best_controls = _df_to_string(best_batch.realization_controls)
+
+    snapshot.assert_match(best_controls, "best_controls")
+    snapshot.assert_match(best_objectives_csv, "best_objectives_csv")
+    snapshot.assert_match(best_objective_gradients_csv, "best_objective_gradients_csv")
+
     # 2DO rewrite for everest storage
     # data = export_data(
     #    export_config=config.export,