Better unit test for the collision system.

collider.cpp

@@ -1,4 +1,7 @@
 #include "collider.hpp"
+#include <fmt/core.h>
+
+using namespace fmt;
 
 using DinkyECS::Entity;
 
@@ -19,8 +22,20 @@ bool SpatialHashTable::occupied(Point at) const {
   return table.contains(at);
 }
 
-inline void find_neighbor(const PointEntityMap &table, FoundList &result, Point at) {
-  auto it = table.find(at);
+/*
+ * Avoid doing work by using the dy,dx and confirming that
+ * at.x or at.y is > 0.  If either is 0 then there can't be
+ * a neighbor since that's out of bounds.
+ */
+inline void find_neighbor(const PointEntityMap &table, FoundList &result, Point at, int dy, int dx) {
+  // don't bother checking for cells out of bounds
+  if((dx < 0 && at.x <= 0) || (dy < 0 && at.y <= 0)) {
+    return;
+  }
+
+  Point cell = {at.x + dx, at.y + dy};
+
+  auto it = table.find(cell);
   if (it != table.end()) {
     result.insert(result.end(), it->second);
   }
@@ -31,16 +46,16 @@ std::tuple<bool, FoundList> SpatialHashTable::neighbors(Point cell, bool diag) c
 
   // just unroll the loop since we only check four directions
   // this also solves the problem that it was detecting that the cell was automatically included as a "neighbor" but it's not
-  find_neighbor(table, result, {cell.x, cell.y+1}); // north
-  find_neighbor(table, result, {cell.x, cell.y-1}); // south
-  find_neighbor(table, result, {cell.x+1, cell.y}); // east
-  find_neighbor(table, result, {cell.x-1, cell.y}); // west
-  find_neighbor(table, result, {cell.x+1, cell.y-1}); // south east
+  find_neighbor(table, result, cell, 0, 1); // north
+  find_neighbor(table, result, cell, 0, -1); // south
+  find_neighbor(table, result, cell, 1, 0); // east
+  find_neighbor(table, result, cell, -1, 0); // west
 
   if(diag) {
-    find_neighbor(table, result, {cell.x-1, cell.y-1}); // south west
-    find_neighbor(table, result, {cell.x+1, cell.y+1}); // north east
-    find_neighbor(table, result, {cell.x-1, cell.y+1}); // north west
+    find_neighbor(table, result, cell, 1, -1); // south east
+    find_neighbor(table, result, cell, -1, -1); // south west
+    find_neighbor(table, result, cell, 1, 1); // north east
+    find_neighbor(table, result, cell, -1, 1); // north west
   }
 
   return std::tuple(!result.empty(), result);