added test for coverage

tests/test_fuel_types.py

@@ -1,6 +1,9 @@
 import pytest
 
-from openmc_plasma_source import get_neutron_energy_distribution
+from openmc_plasma_source import (
+    get_neutron_energy_distribution,
+    get_reactions_from_fuel,
+)
 
 
 @pytest.mark.parametrize(
@@ -45,3 +48,22 @@ def test_fuel_with_incorrect_isotopese(temperature, fuel):
     # Should reject anything which is not 'D' or 'T'.
     with pytest.raises(ValueError):
         get_neutron_energy_distribution(temperature, fuel)
+
+
+@pytest.mark.parametrize(
+    "fuel, expected_output",
+    [
+        ({"D": 1.0}, ["DD"]),
+        ({"T": 1.0}, ["TT"]),
+        ({"T": 0.5, "D": 0.5}, ["DT", "DD", "TT"]),
+        ({"D": 0.2, "T": 0.8}, ["DT", "DD", "TT"]),
+        ({"coucou": 0.2}, None),
+    ],
+)
+def test_get_reactions_from_fuel(fuel, expected_output):
+    """Test the get_reactions_from_fuel function"""
+    if expected_output is None:
+        with pytest.raises(ValueError, match=f"{fuel}"):
+            get_reactions_from_fuel(fuel)
+    else:
+        assert get_reactions_from_fuel(fuel) == expected_output