Add testing and remove iteration none warning

src/ert/libres_facade.py

@@ -128,12 +128,6 @@ def load_from_forward_model(
         realisations: npt.NDArray[np.bool_],
         iteration: Optional[int] = None,
     ) -> int:
-        if iteration is not None:
-            warnings.warn(
-                "The iteration argument has no effect, iteration is read from ensemble",
-                DeprecationWarning,
-                stacklevel=1,
-            )
         t = time.perf_counter()
         run_args = create_run_arguments(
             Runpaths(

tests/ert/unit_tests/test_load_forward_model.py

@@ -10,6 +10,7 @@
 from ert.config import ErtConfig
 from ert.enkf_main import create_run_path
 from ert.libres_facade import LibresFacade
+from ert.run_arg import create_run_arguments
 from ert.storage import open_storage
 
 
@@ -281,3 +282,54 @@ def test_that_the_states_are_set_correctly():
     facade.load_from_forward_model(new_ensemble, realizations, 0)
     assert not new_ensemble.is_initalized()
     assert new_ensemble.has_data()
+
+
+@pytest.mark.parametrize("iter", [None, 0, 1, 2, 3])
+@pytest.mark.usefixtures("use_tmpdir")
+def test_loading_from_any_available_iter(storage, run_paths, run_args, iter):
+    config_text = dedent(
+        """
+    NUM_REALIZATIONS 1
+    GEN_DATA RESPONSE RESULT_FILE:response.out INPUT_FORMAT:ASCII
+        """
+    )
+    Path("config.ert").write_text(config_text, encoding="utf-8")
+
+    ert_config = ErtConfig.from_file("config.ert")
+    prior_ensemble = storage.create_ensemble(
+        storage.create_experiment(
+            responses=ert_config.ensemble_config.response_configuration
+        ),
+        name="prior",
+        ensemble_size=ert_config.model_config.num_realizations,
+        iteration=iter if iter is not None else 0,
+    )
+
+    run_args = create_run_arguments(
+        run_paths(ert_config),
+        [True] * ert_config.model_config.num_realizations,
+        prior_ensemble,
+        iter,
+    )
+    create_run_path(
+        run_args,
+        prior_ensemble,
+        ert_config,
+        run_paths(ert_config),
+    )
+    run_path = Path(
+        f"simulations/realization-0/iter-{iter if iter is not None else 0}/"
+    )
+    with open(run_path / "response.out", "w", encoding="utf-8") as fout:
+        fout.write("\n".join(["1", "2", "3"]))
+    with open(run_path / "response.out_active", "w", encoding="utf-8") as fout:
+        fout.write("\n".join(["1", "0", "1"]))
+
+    facade = LibresFacade.from_config_file("config.ert")
+    facade.load_from_forward_model(prior_ensemble, [True], iter)
+    assert list(
+        prior_ensemble.load_responses("RESPONSE", (0,))
+        .to_dataframe()
+        .dropna()
+        .values.flatten()
+    ) == [1.0, 3.0]