From cfebe16127c0f6636d0370ac141df8a769bebded Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <mail@jshimwell.com>
Date: Thu, 11 Apr 2024 16:35:29 +0100
Subject: [PATCH] added check for length of value passed into EnergyFilter
 (#2887)

---
 openmc/filter.py                 | 4 ++++
 tests/unit_tests/test_filters.py | 7 ++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/openmc/filter.py b/openmc/filter.py
index 04b30261da2..c1d86126a7c 100644
--- a/openmc/filter.py
+++ b/openmc/filter.py
@@ -1377,6 +1377,10 @@ class EnergyFilter(RealFilter):
     """
     units = 'eV'
 
+    def __init__(self, values, filter_id=None):
+        cv.check_length('values', values, 2)
+        super().__init__(values, filter_id)
+
     def get_bin_index(self, filter_bin):
         # Use lower energy bound to find index for RealFilters
         deltas = np.abs(self.bins[:, 1] - filter_bin[1]) / filter_bin[1]
diff --git a/tests/unit_tests/test_filters.py b/tests/unit_tests/test_filters.py
index 4ace59e723e..55bb62075bd 100644
--- a/tests/unit_tests/test_filters.py
+++ b/tests/unit_tests/test_filters.py
@@ -1,6 +1,6 @@
 import numpy as np
 import openmc
-from pytest import fixture, approx
+from pytest import fixture, approx, raises
 
 
 @fixture(scope='module')
@@ -248,6 +248,11 @@ def test_energy():
     assert len(f.values) == 710
 
 
+def test_energyfilter_error_handling():
+    with raises(ValueError):
+        openmc.EnergyFilter([1e6])
+
+
 def test_lethargy_bin_width():
     f = openmc.EnergyFilter.from_group_structure('VITAMIN-J-175')
     assert len(f.lethargy_bin_width) == 175