diff --git a/WFC++/Tiled3D/StandardRunner.h b/WFC++/Tiled3D/StandardRunner.h
index b3f8087..0d111de 100644
--- a/WFC++/Tiled3D/StandardRunner.h
+++ b/WFC++/Tiled3D/StandardRunner.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <span>
+#include <tuple>
 #include "Grid.h"
 
 namespace WFC::Tiled3D
@@ -92,13 +93,25 @@ namespace WFC::Tiled3D
         //Returns whether the algorithm is finished.
         bool TickN(int n);
 
+        void Reset()
+        {
+            Grid.ClearCells(Region3i(Grid.Cells.GetDimensions()));
+            report.Clear();
+            nextCells.Clear();
+            unsolvableCells.Clear();
+        }
+        //TODO: Another overload that takes new 'constants'.
+
 
         StandardRunner(const List<Tile>& inputTiles, const Vector3i& gridSize,
+                       const Dictionary<Vector3i, std::tuple<TileIdx, Transform3D>>* constants = nullptr,
                        PRNG rand = PRNG(std::random_device()()))
             : Grid(inputTiles, gridSize), Rand(rand),
               History(gridSize, { })
         {
-
+            if (constants != nullptr)
+                for (const auto& [cellPos, tileData] : *constants)
+                    Set(cellPos, std::get<0>(tileData), std::get<1>(tileData));
         }
 
 
diff --git a/WFCtests/main.cpp b/WFCtests/main.cpp
index a8efc56..b68cc23 100644
--- a/WFCtests/main.cpp
+++ b/WFCtests/main.cpp
@@ -790,24 +790,26 @@ SUITE(WFC_Tiled3D)
 
     TEST(StandardRunner)
     {
+        //Use two permutations of a single tile,
+        //    which are compatible along Z but not X or Y,
+        //    ensuring that each Z-level uses all one permutation.
+        TransformSet usedTransforms;
+        usedTransforms.Add(Transform3D{ });
+        usedTransforms.Add(Transform3D{ false, Rotations3D::AxisZ_90 });
+        StandardRunner state(OneTileArmy(usedTransforms), {4, 5, 6});
+
         //StandardRunner uses <random> to generate numbers.
         //Run the test many times to cover a broad range of possible outcomes.
         const int N_TESTS =
             #ifdef _DEBUG
-                100000
+                20000
             #else
-                400000
+                200000
             #endif
         ;
         for (int i = 0; i < N_TESTS; ++i)
         {
-            //Use two permutations of a single tile,
-            //    which are compatible along Z but not X or Y,
-            //    ensuring that each Z-level uses all one permutation.
-            TransformSet usedTransforms;
-            usedTransforms.Add(Transform3D{ });
-            usedTransforms.Add(Transform3D{ false, Rotations3D::AxisZ_90 });
-            StandardRunner state(OneTileArmy(usedTransforms), {4, 5, 6});
+            state.Reset();
 
             //Tick once, and check that one cell is set.
             bool isFinished = state.Tick();
@@ -855,6 +857,8 @@ SUITE(WFC_Tiled3D)
                     setCellPos == originalCellPos.MoreY() ||
                     setCellPos == originalCellPos.LessZ() ||
                     setCellPos == originalCellPos.MoreZ());
+
+            //TODO: Set a cell that makes the grid unsolvable, then watch it clear.
         }
     }
 }
@@ -862,5 +866,6 @@ SUITE(WFC_Tiled3D)
 
 int main(int, const char* [])
 {
+    std::cout << "Running..." << std::endl;
     return UnitTest::RunAllTests();
 }
\ No newline at end of file