diff --git a/tests/regression_tests/lattice_multiple/geometry.xml b/tests/regression_tests/lattice_multiple/geometry.xml
deleted file mode 100644
index f6f067aadd..0000000000
--- a/tests/regression_tests/lattice_multiple/geometry.xml
+++ /dev/null
@@ -1,181 +0,0 @@
-<?xml version="1.0"?>
-<geometry>
-
-  <surface id="1" type="z-cylinder" coeffs="0. 0. 0.41" />
-  <surface id="2" type="z-cylinder" coeffs="0. 0. 0.475" />
-  <surface id="3" type="z-cylinder" coeffs="0. 0. 0.56" />
-  <surface id="4" type="z-cylinder" coeffs="0. 0. 0.62" />
-  <surface id="5" type="z-cylinder" coeffs="0. 0. 187.6" />
-  <surface id="6" type="z-cylinder" coeffs="0. 0. 209.0" />
-  <surface id="7" type="z-cylinder" coeffs="0. 0. 229.0" />
-  <surface id="8" type="z-cylinder" coeffs="0. 0. 249.0" boundary="vacuum" />
-
-  <surface id="31" type="z-plane" coeffs="-229.0" boundary="vacuum" />
-  <surface id="32" type="z-plane" coeffs="-199.0" />
-  <surface id="33" type="z-plane" coeffs="-193.0" />
-  <surface id="34" type="z-plane" coeffs="-183.0" />
-  <surface id="35" type="z-plane" coeffs="0.0" />
-  <surface id="36" type="z-plane" coeffs="183.0" />
-  <surface id="37" type="z-plane" coeffs="203.0" />
-  <surface id="38" type="z-plane" coeffs="215.0" />
-  <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
-
-  <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
-
-  <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" region="-1"   />
-  <cell id="22" universe="1" material="2" region="1 -2" />
-  <cell id="23" universe="1" material="3" region="2"    />
-
-  <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" region="-3"   />
-  <cell id="25" universe="2" material="2" region="3 -4" />
-  <cell id="26" universe="2" material="3" region="4"    />
-
-  <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" region="-1"   />
-  <cell id="28" universe="3" material="2" region="1 -2" />
-  <cell id="29" universe="3" material="4" region="2"    />
-
-  <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" region="-3"   />
-  <cell id="31" universe="4" material="2" region="3 -4" />
-  <cell id="32" universe="4" material="4" region="4"    />
-
-  <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" region="34 -35" />
-
-  <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   region="34 -35" />
-
-  <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" region="35 -36" />
-
-  <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   region="35 -36" />
-
-  <!-- Fuel Assembly (Lower Half) -->
-  <lattice id="100">
-    <dimension>17 17</dimension>
-    <lower_left>-10.71 -10.71</lower_left>
-    <pitch>1.26 1.26</pitch>
-    <universes>
-      1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-      1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-      1 1 1 1 1 2 1 1 2 1 1 2 1 1 1 1 1
-      1 1 1 2 1 1 1 1 1 1 1 1 1 2 1 1 1
-      1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-      1 1 2 1 1 2 1 1 2 1 1 2 1 1 2 1 1
-      1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-      1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-      1 1 2 1 1 2 1 1 2 1 1 2 1 1 2 1 1
-      1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-      1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-      1 1 2 1 1 2 1 1 2 1 1 2 1 1 2 1 1
-      1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-      1 1 1 2 1 1 1 1 1 1 1 1 1 2 1 1 1
-      1 1 1 1 1 2 1 1 2 1 1 2 1 1 1 1 1
-      1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-      1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-    </universes>
-  </lattice>
-
-  <!-- Fuel Assembly (Upper Half) -->
-  <lattice id="101">
-    <dimension>17 17</dimension>
-    <lower_left>-10.71 -10.71</lower_left>
-    <pitch>1.26 1.26</pitch>
-    <universes>
-      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
-      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
-      3 3 3 3 3 4 3 3 4 3 3 4 3 3 3 3 3
-      3 3 3 4 3 3 3 3 3 3 3 3 3 4 3 3 3
-      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
-      3 3 4 3 3 4 3 3 4 3 3 4 3 3 4 3 3
-      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
-      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
-      3 3 4 3 3 4 3 3 4 3 3 4 3 3 4 3 3
-      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
-      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
-      3 3 4 3 3 4 3 3 4 3 3 4 3 3 4 3 3
-      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
-      3 3 3 4 3 3 3 3 3 3 3 3 3 4 3 3 3
-      3 3 3 3 3 4 3 3 4 3 3 4 3 3 3 3 3
-      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
-      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
-    </universes>
-  </lattice>
-
-  <!-- Core Lattice (Lower Half) -->
-  <lattice id="200">
-    <dimension>21 21</dimension>
-    <lower_left>-224.91 -224.91</lower_left>
-    <pitch>21.42 21.42</pitch>
-    <universes>
-      5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5
-      5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5
-      5 5 5 5 5 5 5 6 6 6 6 6 6 6 5 5 5 5 5 5 5
-      5 5 5 5 5 6 6 6 6 6 6 6 6 6 6 6 5 5 5 5 5
-      5 5 5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5 5 5
-      5 5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5 5
-      5 5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5 5
-      5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5
-      5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5
-      5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5
-      5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5
-      5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5
-      5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5
-      5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5
-      5 5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5 5
-      5 5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5 5
-      5 5 5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5 5 5
-      5 5 5 5 5 6 6 6 6 6 6 6 6 6 6 6 5 5 5 5 5
-      5 5 5 5 5 5 5 6 6 6 6 6 6 6 5 5 5 5 5 5 5
-      5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5
-      5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5
-    </universes>
-  </lattice>
-
-  <!-- Core Lattice (Upper Half) -->
-  <lattice id="201">
-    <dimension>21 21</dimension>
-    <lower_left>-224.91 -224.91</lower_left>
-    <pitch>21.42 21.42</pitch>
-    <universes>
-      7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7
-      7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7
-      7 7 7 7 7 7 7 8 8 8 8 8 8 8 7 7 7 7 7 7 7
-      7 7 7 7 7 8 8 8 8 8 8 8 8 8 8 8 7 7 7 7 7
-      7 7 7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7 7 7
-      7 7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7 7
-      7 7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7 7
-      7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7
-      7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7
-      7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7
-      7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7
-      7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7
-      7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7
-      7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7
-      7 7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7 7
-      7 7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7 7
-      7 7 7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 7 7 7 7
-      7 7 7 7 7 8 8 8 8 8 8 8 8 8 8 8 7 7 7 7 7
-      7 7 7 7 7 7 7 8 8 8 8 8 8 8 7 7 7 7 7 7 7
-      7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7
-      7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7
-    </universes>
-  </lattice>
-
-</geometry>
diff --git a/tests/regression_tests/lattice_multiple/inputs_true.dat b/tests/regression_tests/lattice_multiple/inputs_true.dat
new file mode 100644
index 0000000000..c92e841bc9
--- /dev/null
+++ b/tests/regression_tests/lattice_multiple/inputs_true.dat
@@ -0,0 +1,53 @@
+<?xml version='1.0' encoding='utf-8'?>
+<geometry>
+  <cell id="1" material="1" region="-1" universe="1" />
+  <cell id="2" material="2" region="1" universe="1" />
+  <cell id="3" material="1" region="-2" universe="2" />
+  <cell id="4" material="2" region="2" universe="2" />
+  <cell fill="3" id="5" universe="4" />
+  <cell fill="5" id="6" region="3 -4 5 -6" universe="6" />
+  <lattice id="3">
+    <pitch>1.2 1.2</pitch>
+    <outer>1</outer>
+    <dimension>2 2</dimension>
+    <lower_left>-1.2 -1.2</lower_left>
+    <universes>
+2 1 
+1 1 </universes>
+  </lattice>
+  <lattice id="5">
+    <pitch>2.4 2.4</pitch>
+    <dimension>2 2</dimension>
+    <lower_left>-2.4 -2.4</lower_left>
+    <universes>
+4 4 
+4 4 </universes>
+  </lattice>
+  <surface coeffs="0.0 0.0 0.4" id="1" type="z-cylinder" />
+  <surface coeffs="0.0 0.0 0.5" id="2" type="z-cylinder" />
+  <surface boundary="reflective" coeffs="-2.4" id="3" name="minimum x" type="x-plane" />
+  <surface boundary="reflective" coeffs="2.4" id="4" name="maximum x" type="x-plane" />
+  <surface boundary="reflective" coeffs="-2.4" id="5" name="minimum y" type="y-plane" />
+  <surface boundary="reflective" coeffs="2.4" id="6" name="maximum y" type="y-plane" />
+</geometry>
+<?xml version='1.0' encoding='utf-8'?>
+<materials>
+  <material depletable="true" id="1" name="UO2">
+    <density units="g/cm3" value="10.0" />
+    <nuclide ao="1.0" name="U235" />
+    <nuclide ao="2.0" name="O16" />
+  </material>
+  <material id="2" name="light water">
+    <density units="g/cm3" value="1.0" />
+    <nuclide ao="2.0" name="H1" />
+    <nuclide ao="1.0" name="O16" />
+    <sab name="c_H_in_H2O" />
+  </material>
+</materials>
+<?xml version='1.0' encoding='utf-8'?>
+<settings>
+  <run_mode>eigenvalue</run_mode>
+  <particles>1000</particles>
+  <batches>10</batches>
+  <inactive>5</inactive>
+</settings>
diff --git a/tests/regression_tests/lattice_multiple/materials.xml b/tests/regression_tests/lattice_multiple/materials.xml
deleted file mode 100644
index 8021f5f99e..0000000000
--- a/tests/regression_tests/lattice_multiple/materials.xml
+++ /dev/null
@@ -1,270 +0,0 @@
-<?xml version="1.0"?>
-<materials>
-
-  <!-- Fuel composition -->
-  <material id="1">
-    <density value="10.062" units="g/cm3" />
-    <nuclide name="U234"   ao="4.9476e-6" />
-    <nuclide name="U235"   ao="4.8218e-4" />
-    <nuclide name="U236"   ao="9.0402e-5" />
-    <nuclide name="U238"   ao="2.1504e-2" />
-    <nuclide name="Np237"  ao="7.3733e-6" />
-    <nuclide name="Pu238"  ao="1.5148e-6" />
-    <nuclide name="Pu239"  ao="1.3955e-4" />
-    <nuclide name="Pu240"  ao="3.4405e-5" />
-    <nuclide name="Pu241"  ao="2.1439e-5" />
-    <nuclide name="Pu242"  ao="3.7422e-6" />
-    <nuclide name="Am241"  ao="4.5041e-7" />
-    <nuclide name="Am242_m1" ao="9.2301e-9" />
-    <nuclide name="Am243"  ao="4.7878e-7" />
-    <nuclide name="Cm242"  ao="1.0485e-7" />
-    <nuclide name="Cm243"  ao="1.4268e-9" />
-    <nuclide name="Cm244"  ao="8.8756e-8" />
-    <nuclide name="Cm245"  ao="3.5285e-9" />
-    <nuclide name="Mo95"   ao="2.6497e-5" />
-    <nuclide name="Tc99"   ao="3.2772e-5" />
-    <nuclide name="Ru101"  ao="3.0742e-5" />
-    <nuclide name="Ru103"  ao="2.3505e-6" />
-    <nuclide name="Ag109"  ao="2.0009e-6" />
-    <nuclide name="Xe135"  ao="1.0801e-8" />
-    <nuclide name="Cs133"  ao="3.4612e-5" />
-    <nuclide name="Nd143"  ao="2.6078e-5" />
-    <nuclide name="Nd145"  ao="1.9898e-5" />
-    <nuclide name="Sm147"  ao="1.6128e-6" />
-    <nuclide name="Sm149"  ao="1.1627e-7" />
-    <nuclide name="Sm150"  ao="7.1727e-6" />
-    <nuclide name="Sm151"  ao="5.4947e-7" />
-    <nuclide name="Sm152"  ao="3.0221e-6" />
-    <nuclide name="Eu153"  ao="2.6209e-6" />
-    <nuclide name="Gd155"  ao="1.5369e-9" />
-    <nuclide name="O16"    ao="4.5737e-2" />
-  </material>
-
-  <!-- Cladding composition -->
-  <material id="2">
-    <density value="5.77" units="g/cm3" />
-    <nuclide name="Zr90" ao="0.5145" />
-    <nuclide name="Zr91" ao="0.1122" />
-    <nuclide name="Zr92" ao="0.1715" />
-    <nuclide name="Zr94" ao="0.1738" />
-    <nuclide name="Zr96" ao="0.0280" />
-  </material>
-
-  <!-- Cold borated water -->
-  <material id="3">
-    <density value="0.07416" units="atom/b-cm" />
-    <nuclide name="H1" ao="2.0" />
-    <nuclide name="O16" ao="1.0" />
-    <nuclide name="B10" ao="6.490e-4" />
-    <nuclide name="B11" ao="2.689e-3" />
-    <sab name="c_H_in_H2O" />
-  </material>
-
-  <!-- Hot borated water -->
-  <material id="4">
-    <density value="0.06614" units="atom/b-cm" />
-    <nuclide name="H1"  ao="2.0" />
-    <nuclide name="O16" ao="1.0" />
-    <nuclide name="B10" ao="6.490e-4" />
-    <nuclide name="B11" ao="2.689e-3" />
-    <sab name="c_H_in_H2O" />
-  </material>
-
-  <!-- RPV Composition -->
-  <material id="5">
-    <density value="7.9" units="g/cm3" />
-    <nuclide name="Fe54"  wo="0.05437098" />
-    <nuclide name="Fe56"  wo="0.88500663" />
-    <nuclide name="Fe57"  wo="0.0208008" />
-    <nuclide name="Fe58"  wo="0.00282159" />
-    <nuclide name="Ni58"  wo="0.0067198" />
-    <nuclide name="Ni60"  wo="0.0026776" />
-    <nuclide name="Ni61"  wo="0.0001183" />
-    <nuclide name="Ni62"  wo="0.0003835" />
-    <nuclide name="Ni64"  wo="0.0001008" />
-    <nuclide name="Mn55"  wo="0.01" />
-    <nuclide name="Mo92"  wo="0.000849" />
-    <nuclide name="Mo94"  wo="0.0005418" />
-    <nuclide name="Mo95"  wo="0.0009438" />
-    <nuclide name="Mo96"  wo="0.0010002" />
-    <nuclide name="Mo97"  wo="0.0005796" />
-    <nuclide name="Mo98"  wo="0.0014814" />
-    <nuclide name="Mo100" wo="0.0006042" />
-    <nuclide name="Si28"  wo="0.00367464" />
-    <nuclide name="Si29"  wo="0.00019336" />
-    <nuclide name="Si30"  wo="0.000132" />
-    <nuclide name="Cr50"  wo="0.00010435" />
-    <nuclide name="Cr52"  wo="0.002092475" />
-    <nuclide name="Cr53"  wo="0.00024185" />
-    <nuclide name="Cr54"  wo="6.1325e-05" />
-    <nuclide name="C0"  wo="0.0025" />
-    <nuclide name="Cu63"  wo="0.0013696" />
-    <nuclide name="Cu65"  wo="0.0006304" />
-  </material>
-
-  <!-- Lower radial reflector -->
-  <material id="6">
-    <density value="4.32" units="g/cm3" />
-    <nuclide name="H1"   wo="0.0095661" />
-    <nuclide name="O16"  wo="0.0759107" />
-    <nuclide name="B10"  wo="3.08409e-5" />
-    <nuclide name="B11"  wo="1.40499e-4" />
-    <nuclide name="Fe54" wo="0.035620772088" />
-    <nuclide name="Fe56" wo="0.579805982228" />
-    <nuclide name="Fe57" wo="0.01362750048" />
-    <nuclide name="Fe58" wo="0.001848545204" />
-    <nuclide name="Ni58" wo="0.055298376566" />
-    <nuclide name="Ni60" wo="0.022034425592" />
-    <nuclide name="Ni61" wo="0.000973510811" />
-    <nuclide name="Ni62" wo="0.003155886695" />
-    <nuclide name="Ni64" wo="0.000829500336" />
-    <nuclide name="Mn55" wo="0.0182870" />
-    <nuclide name="Si28" wo="0.00839976771" />
-    <nuclide name="Si29" wo="0.00044199679" />
-    <nuclide name="Si30" wo="0.0003017355" />
-    <nuclide name="Cr50" wo="0.007251360806" />
-    <nuclide name="Cr52" wo="0.145407678031" />
-    <nuclide name="Cr53" wo="0.016806340306" />
-    <nuclide name="Cr54" wo="0.004261520857" />
-    <sab name="c_H_in_H2O" />
-  </material>
-
-  <!-- Upper radial reflector / Top plate region -->
-  <material id="7">
-    <density value="4.28" units="g/cm3" />
-    <nuclide name="H1"   wo="0.0086117" />
-    <nuclide name="O16"  wo="0.0683369" />
-    <nuclide name="B10"  wo="2.77638e-5" />
-    <nuclide name="B11"  wo="1.26481e-4" />
-    <nuclide name="Fe54" wo="0.035953677186" />
-    <nuclide name="Fe56" wo="0.585224740891" />
-    <nuclide name="Fe57" wo="0.01375486056" />
-    <nuclide name="Fe58" wo="0.001865821363" />
-    <nuclide name="Ni58" wo="0.055815129186" />
-    <nuclide name="Ni60" wo="0.022240333032" />
-    <nuclide name="Ni61" wo="0.000982608081" />
-    <nuclide name="Ni62" wo="0.003185377845" />
-    <nuclide name="Ni64" wo="0.000837251856" />
-    <nuclide name="Mn55" wo="0.0184579" />
-    <nuclide name="Si28" wo="0.00847831314" />
-    <nuclide name="Si29" wo="0.00044612986" />
-    <nuclide name="Si30" wo="0.000304557" />
-    <nuclide name="Cr50" wo="0.00731912987" />
-    <nuclide name="Cr52" wo="0.146766614995" />
-    <nuclide name="Cr53" wo="0.01696340737" />
-    <nuclide name="Cr54" wo="0.004301347765" />
-    <sab name="c_H_in_H2O" />
-  </material>
-
-  <!-- Bottom plate region -->
-  <material id="8">
-    <density value="7.184" units="g/cm3" />
-    <nuclide name="H1"   wo="0.0011505" />
-    <nuclide name="O16"  wo="0.0091296" />
-    <nuclide name="B10"  wo="3.70915e-6" />
-    <nuclide name="B11"  wo="1.68974e-5" />
-    <nuclide name="Fe54" wo="0.03855611055" />
-    <nuclide name="Fe56" wo="0.627585036425" />
-    <nuclide name="Fe57" wo="0.014750478" />
-    <nuclide name="Fe58" wo="0.002000875025" />
-    <nuclide name="Ni58" wo="0.059855207342" />
-    <nuclide name="Ni60" wo="0.023850159704" />
-    <nuclide name="Ni61" wo="0.001053732407" />
-    <nuclide name="Ni62" wo="0.003415945715" />
-    <nuclide name="Ni64" wo="0.000897854832" />
-    <nuclide name="Mn55" wo="0.0197940" />
-    <nuclide name="Si28" wo="0.00909197802" />
-    <nuclide name="Si29" wo="0.00047842098" />
-    <nuclide name="Si30" wo="0.000326601" />
-    <nuclide name="Cr50" wo="0.007848910646" />
-    <nuclide name="Cr52" wo="0.157390026871" />
-    <nuclide name="Cr53" wo="0.018191270146" />
-    <nuclide name="Cr54" wo="0.004612692337" />
-    <sab name="c_H_in_H2O" />
-  </material>
-
-  <!-- Bottom nozzle region -->
-  <material id="9">
-    <density value="2.53" units="g/cm3" />
-    <nuclide name="H1"   wo="0.0245014" />
-    <nuclide name="O16"  wo="0.1944274" />
-    <nuclide name="B10"  wo="7.89917e-5" />
-    <nuclide name="B11"  wo="3.59854e-4" />
-    <nuclide name="Fe54" wo="0.030411411144" />
-    <nuclide name="Fe56" wo="0.495012237964" />
-    <nuclide name="Fe57" wo="0.01163454624" />
-    <nuclide name="Fe58" wo="0.001578204652" />
-    <nuclide name="Ni58" wo="0.047211231662" />
-    <nuclide name="Ni60" wo="0.018811987544" />
-    <nuclide name="Ni61" wo="0.000831139127" />
-    <nuclide name="Ni62" wo="0.002694352115" />
-    <nuclide name="Ni64" wo="0.000708189552" />
-    <nuclide name="Mn55" wo="0.0156126" />
-    <nuclide name="Si28" wo="0.007171335558" />
-    <nuclide name="Si29" wo="0.000377356542" />
-    <nuclide name="Si30" wo="0.0002576079" />
-    <nuclide name="Cr50" wo="0.006190885148" />
-    <nuclide name="Cr52" wo="0.124142524198" />
-    <nuclide name="Cr53" wo="0.014348496148" />
-    <nuclide name="Cr54" wo="0.003638294506" />
-    <sab name="c_H_in_H2O" />
-  </material>
-
-  <!-- Top nozzle region -->
-  <material id="10">
-    <density value="1.746" units="g/cm3" />
-    <nuclide name="H1"   wo="0.0358870" />
-    <nuclide name="O16"  wo="0.2847761" />
-    <nuclide name="B10"  wo="1.15699e-4" />
-    <nuclide name="B11"  wo="5.27075e-4" />
-    <nuclide name="Fe54" wo="0.02644016154" />
-    <nuclide name="Fe56" wo="0.43037146399" />
-    <nuclide name="Fe57" wo="0.0101152584" />
-    <nuclide name="Fe58" wo="0.00137211607" />
-    <nuclide name="Ni58" wo="0.04104621835" />
-    <nuclide name="Ni60" wo="0.0163554502" />
-    <nuclide name="Ni61" wo="0.000722605975" />
-    <nuclide name="Ni62" wo="0.002342513875" />
-    <nuclide name="Ni64" wo="0.0006157116" />
-    <nuclide name="Mn55" wo="0.0135739" />
-    <nuclide name="Si28" wo="0.006234853554" />
-    <nuclide name="Si29" wo="0.000328078746" />
-    <nuclide name="Si30" wo="0.0002239677" />
-    <nuclide name="Cr50" wo="0.005382452306" />
-    <nuclide name="Cr52" wo="0.107931450781" />
-    <nuclide name="Cr53" wo="0.012474806806" />
-    <nuclide name="Cr54" wo="0.003163190107" />
-    <sab name="c_H_in_H2O" />
-  </material>
-
-  <!-- Top of Fuel Assemblies -->
-  <material id="11">
-    <density value="3.044" units="g/cm3" />
-    <nuclide name="H1"   wo="0.0162913" />
-    <nuclide name="O16"  wo="0.1292776" />
-    <nuclide name="B10"  wo="5.25228e-5" />
-    <nuclide name="B11"  wo="2.39272e-4" />
-    <nuclide name="Zr90" wo="0.43313403903" />
-    <nuclide name="Zr91" wo="0.09549277374" />
-    <nuclide name="Zr92" wo="0.14759527104" />
-    <nuclide name="Zr94" wo="0.15280552077" />
-    <nuclide name="Zr96" wo="0.02511169542" />
-    <sab name="c_H_in_H2O" />
-  </material>
-
-  <!-- Bottom of Fuel Assemblies -->
-  <material id="12">
-    <density value="1.762" units="g/cm3" />
-    <nuclide name="H1"   wo="0.0292856" />
-    <nuclide name="O16"  wo="0.2323919" />
-    <nuclide name="B10"  wo="9.44159e-5" />
-    <nuclide name="B11"  wo="4.30120e-4" />
-    <nuclide name="Zr90" wo="0.3741373658" />
-    <nuclide name="Zr91" wo="0.0824858164" />
-    <nuclide name="Zr92" wo="0.1274914944" />
-    <nuclide name="Zr94" wo="0.1319920622" />
-    <nuclide name="Zr96" wo="0.0216912612" />
-    <sab name="c_H_in_H2O" />
-  </material>
-
-</materials>
diff --git a/tests/regression_tests/lattice_multiple/results_true.dat b/tests/regression_tests/lattice_multiple/results_true.dat
index d5d4bd4cc8..c1fa5321bf 100644
--- a/tests/regression_tests/lattice_multiple/results_true.dat
+++ b/tests/regression_tests/lattice_multiple/results_true.dat
@@ -1,2 +1,2 @@
 k-combined:
-9.581522E-01 4.261828E-02
+1.831313E+00 6.958576E-04
diff --git a/tests/regression_tests/lattice_multiple/settings.xml b/tests/regression_tests/lattice_multiple/settings.xml
deleted file mode 100644
index 569c809821..0000000000
--- a/tests/regression_tests/lattice_multiple/settings.xml
+++ /dev/null
@@ -1,18 +0,0 @@
-<?xml version="1.0"?>
-<settings>
-
-  <run_mode>eigenvalue</run_mode>
-  <batches>10</batches>
-  <inactive>5</inactive>
-  <particles>100</particles>
-
-  <source>
-    <space type="box">
-      <parameters>
-        -160 -160 -183
-         160  160  183
-      </parameters>
-    </space>
-  </source>
-
-</settings>
diff --git a/tests/regression_tests/lattice_multiple/test.py b/tests/regression_tests/lattice_multiple/test.py
index f0672d9a4e..a9b15c9c85 100644
--- a/tests/regression_tests/lattice_multiple/test.py
+++ b/tests/regression_tests/lattice_multiple/test.py
@@ -1,6 +1,62 @@
-from tests.testing_harness import TestHarness
+import numpy as np
+import openmc
+import pytest
+
+from tests.testing_harness import PyAPITestHarness
 
 
-def test_lattice_multiple():
-    harness = TestHarness('statepoint.10.h5')
+@pytest.fixture
+def model():
+    model = openmc.model.Model()
+
+    uo2 = openmc.Material(name='UO2')
+    uo2.set_density('g/cm3', 10.0)
+    uo2.add_nuclide('U235', 1.0)
+    uo2.add_nuclide('O16', 2.0)
+    water = openmc.Material(name='light water')
+    water.add_nuclide('H1', 2.0)
+    water.add_nuclide('O16', 1.0)
+    water.set_density('g/cm3', 1.0)
+    water.add_s_alpha_beta('c_H_in_H2O')
+    model.materials.extend([uo2, water])
+
+    cyl = openmc.ZCylinder(r=0.4)
+    big_cyl = openmc.ZCylinder(r=0.5)
+    c1 = openmc.Cell(fill=uo2, region=-cyl)
+    c2 = openmc.Cell(fill=water, region=+cyl)
+    pin = openmc.Universe(cells=[c1, c2])
+    c3 = openmc.Cell(fill=uo2, region=-big_cyl)
+    c4 = openmc.Cell(fill=water, region=+big_cyl)
+    big_pin = openmc.Universe(cells=[c3, c4])
+
+    d = 1.2
+    inner_lattice = openmc.RectLattice()
+    inner_lattice.lower_left = (-d, -d)
+    inner_lattice.pitch = (d, d)
+    inner_lattice.outer = pin
+    inner_lattice.universes = [
+        [big_pin, pin],
+        [pin, pin],
+    ]
+    inner_cell = openmc.Cell(fill=inner_lattice)
+    inner_univ = openmc.Universe(cells=[inner_cell])
+
+    lattice = openmc.RectLattice()
+    lattice.lower_left = (-2*d, -2*d)
+    lattice.pitch = (2*d, 2*d)
+    lattice.universes = np.full((2, 2), inner_univ)
+
+    box = openmc.model.rectangular_prism(4*d, 4*d, boundary_type='reflective')
+    main_cell = openmc.Cell(fill=lattice, region=box)
+    model.geometry = openmc.Geometry([main_cell])
+
+    model.settings.batches = 10
+    model.settings.inactive = 5
+    model.settings.particles = 1000
+
+    return model
+
+
+def test_lattice_multiple(model):
+    harness = PyAPITestHarness('statepoint.10.h5', model)
     harness.main()