Adding to regression test instead of making new unit test

tests/regression_tests/statepoint_restart/test.py

@@ -1,11 +1,14 @@
 import glob
 import os
+from pathlib import Path
 
 import openmc
 
 from tests.testing_harness import TestHarness
 from tests.regression_tests import config
+from tests import cdtemp
 
+import pytest
 
 class StatepointRestartTestHarness(TestHarness):
     def __init__(self, final_sp, restart_sp):
@@ -59,3 +62,27 @@ def test_statepoint_restart():
     harness = StatepointRestartTestHarness('statepoint.10.h5',
                                            'statepoint.07.h5')
     harness.main()
+
+
+def test_batch_check(request):
+    xmls = glob.glob('*.xml')
+    xmls = [request.fspath.dirpath() / Path(f) for f in xmls]
+
+    with cdtemp(xmls):
+        model = openmc.Model.from_xml()
+        model.settings.particles = 100
+        # run the model
+        sp_file = model.run()
+
+        # run a restart with the resulting statepoint
+        # and the settings unchanged
+        with pytest.raises(RuntimeError, match='is smaller than the number of batches'):
+            model.run(restart_file=sp_file)
+
+        # update the number of batches and run again
+        model.settings.batches = 15
+        model.settings.statepoint = {}
+        sp_file = model.run(restart_file=sp_file)
+
+        sp = openmc.StatePoint(sp_file)
+        assert sp.n_batches == 15