First cut of pulling out the relevant parts of my original game to make a little framework.

tests/lighting.cpp

@@ -0,0 +1,42 @@
+#include <catch2/catch_test_macros.hpp>
+#include <fmt/core.h>
+#include <nlohmann/json.hpp>
+#include <fstream>
+#include "game/map.hpp"
+#include "game/level.hpp"
+#include "graphics/lights.hpp"
+#include "algos/point.hpp"
+
+using namespace lighting;
+
+TEST_CASE("lighting a map works", "[lighting]") {
+  GameDB::init();
+  auto& level = GameDB::current_level();
+  auto& map = *level.map;
+
+  Point light1, light2;
+
+  REQUIRE(map.place_entity(0, light1));
+  REQUIRE(map.place_entity(0, light1));
+
+  LightSource source1{6, 1.0};
+  LightSource source2{4,3};
+
+  LightRender lr(map.walls());
+
+  lr.reset_light();
+
+  lr.set_light_target(light1);
+  lr.set_light_target(light2);
+
+  lr.path_light(map.walls());
+
+  lr.render_light(source1, light1);
+  lr.render_light(source2, light2);
+
+  lr.clear_light_target(light1);
+  lr.clear_light_target(light2);
+
+  Matrix &lighting = lr.lighting();
+  (void)lighting;
+}