diff --git a/src/openmc_plasma_source/fuel_types.py b/src/openmc_plasma_source/fuel_types.py
index 45e6ac6..2b50426 100644
--- a/src/openmc_plasma_source/fuel_types.py
+++ b/src/openmc_plasma_source/fuel_types.py
@@ -52,7 +52,7 @@ def get_neutron_energy_distribution(
     # print("DTmean", DTmean)
     DDmean, DDvar = nst.DDprimspecmoments(ion_temperature_kev)
     # print("DDmean", DDmean)
-    #todo make use of these DTvar and DDvar values in muir or gaussian distribution
+    # todo make use of these DTvar and DDvar values in muir or gaussian distribution
 
     if ["D", "T"] == sorted(set(fuel.keys())):
 
@@ -66,8 +66,8 @@ def get_neutron_energy_distribution(
 
         dNdE_TT = strength_TT * nst.dNdE_TT(E_pspec, ion_temperature_kev)
         tt_source = openmc.stats.Tabular(E_pspec * 1e6, dNdE_TT)
-        dd_source = openmc.stats.muir(e0=DDmean*1e6, m_rat=4, kt=ion_temperature)
-        dt_source = openmc.stats.muir(e0=DTmean*1e6, m_rat=5, kt=ion_temperature)
+        dd_source = openmc.stats.muir(e0=DDmean * 1e6, m_rat=4, kt=ion_temperature)
+        dt_source = openmc.stats.muir(e0=DTmean * 1e6, m_rat=5, kt=ion_temperature)
         # todo look into combining distributions openmc.data.combine_distributions()
         return [tt_source, dd_source, dt_source], [
             strength_TT,
@@ -78,7 +78,7 @@ def get_neutron_energy_distribution(
     elif ["D"] == sorted(set(fuel.keys())):
 
         strength_DD = 1.0
-        dd_source = openmc.stats.muir(e0=DDmean*1e6, m_rat=4, kt=ion_temperature)
+        dd_source = openmc.stats.muir(e0=DDmean * 1e6, m_rat=4, kt=ion_temperature)
         return [dd_source], [strength_DD]
 
     elif ["T"] == sorted(set(fuel.keys())):
diff --git a/tests/test_fuel_types.py b/tests/test_fuel_types.py
index 17dc1c5..b0a2c8a 100644
--- a/tests/test_fuel_types.py
+++ b/tests/test_fuel_types.py
@@ -3,35 +3,44 @@
 from openmc_plasma_source import get_neutron_energy_distribution
 
 
-@pytest.mark.parametrize("temperature, fuel", [
-    (2e3, {'D': 1.}),
-    (2e3, {'T': 1.}),
-    (2e3, {'T': 0.5, 'D': 0.5}),
-    (2e3, {'T': 0.2, 'D': 0.8}),
-])
+@pytest.mark.parametrize(
+    "temperature, fuel",
+    [
+        (2e3, {"D": 1.0}),
+        (2e3, {"T": 1.0}),
+        (2e3, {"T": 0.5, "D": 0.5}),
+        (2e3, {"T": 0.2, "D": 0.8}),
+    ],
+)
 def test_fuel_with_correct_inputs(temperature, fuel):
     # Should accept any non-zero positive inputs to either variable
     get_neutron_energy_distribution(temperature, fuel)
 
 
-@pytest.mark.parametrize("temperature, fuel", [
-    (2e3, {'D': 1.1}),
-    (2e3, {'T': 0.9}),
-    (2e3, {'T': -0.5, 'D': 0.5}),
-    (2e3, {'T': -0.2, 'D': -0.8}),
-])
+@pytest.mark.parametrize(
+    "temperature, fuel",
+    [
+        (2e3, {"D": 1.1}),
+        (2e3, {"T": 0.9}),
+        (2e3, {"T": -0.5, "D": 0.5}),
+        (2e3, {"T": -0.2, "D": -0.8}),
+    ],
+)
 def test_fuel_with_bad_inputs(temperature, fuel):
     # Should reject any negative numbers and zeros.
     with pytest.raises(ValueError):
         get_neutron_energy_distribution(temperature, fuel)
 
 
-@pytest.mark.parametrize("temperature, fuel", [
-    (2e3, {'DD': 1.1}),
-    (2e3, {'DT': 0.9}),
-    (2e3, {'He3': -0.5, 'D': 0.5}),
-    (2e3, {1: -0.2, 'D': -0.8}),
-])
+@pytest.mark.parametrize(
+    "temperature, fuel",
+    [
+        (2e3, {"DD": 1.1}),
+        (2e3, {"DT": 0.9}),
+        (2e3, {"He3": -0.5, "D": 0.5}),
+        (2e3, {1: -0.2, "D": -0.8}),
+    ],
+)
 def test_fuel_with_incorrect_isotopese(temperature, fuel):
     # Should reject anything which is not 'D' or 'T'.
     with pytest.raises(ValueError):