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

tests/map.cpp

@@ -0,0 +1,85 @@
+#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 "game/systems.hpp"
+#include <cmath>
+#include "graphics/textures.hpp"
+#include "algos/rand.hpp"
+
+using namespace fmt;
+using namespace nlohmann;
+using std::string;
+
+json load_test_data(const string &fname) {
+  std::ifstream infile(fname);
+  return json::parse(infile);
+}
+
+TEST_CASE("camera control", "[map]") {
+  GameDB::init();
+
+  auto& level = GameDB::current_level();
+  auto& map = *level.map;
+
+  Point center = map.center_camera({10,10}, 5, 5);
+
+  // map.dump(center.x, center.y);
+  REQUIRE(center.x == 8);
+  REQUIRE(center.y == 8);
+
+  Point translation = map.map_to_camera({10,10}, center);
+
+  REQUIRE(translation.x == 2);
+  REQUIRE(translation.y == 2);
+}
+
+TEST_CASE("map placement test", "[map-fail]") {
+  GameDB::init();
+
+  for(int i = 0; i < 10; i++) {
+    auto& level = GameDB::create_level();
+
+    for(size_t rnum = 0; rnum < level.map->room_count(); rnum++) {
+      Point pos;
+
+      REQUIRE(level.map->place_entity(rnum, pos));
+
+      REQUIRE(!level.map->iswall(pos.x, pos.y));
+      REQUIRE(level.map->inmap(pos.x, pos.y));
+    }
+  }
+}
+
+TEST_CASE("map image test", "[map]") {
+  GameDB::init();
+
+  auto& level = GameDB::current_level();
+  Matrix map_tiles = matrix::make(7,7);
+  EntityGrid entity_map;
+
+  auto render = std::make_shared<sf::RenderTexture>();
+  sf::Sprite sprite{render->getTexture()};
+  auto player = level.world->get_the<components::Player>();
+  auto& player_pos = level.world->get<components::Position>(player.entity);
+  auto player_display = level.world->get<components::Tile>(player.entity).display;
+
+  for(matrix::each_row it{level.map->walls()}; it.next();) {
+    player_pos.location.x = it.x;
+    player_pos.location.y = it.y;
+    System::draw_map(map_tiles, entity_map);
+    System::render_map(map_tiles, entity_map, *render, 2, player_display);
+
+    // randomly test about 80% of them
+    if(Random::uniform(0, 100) < 20) break;
+
+#ifdef TEST_RENDER
+    // confirm we get two different maps
+    auto out_img = render->getTexture().copyToImage();
+    bool worked = out_img.saveToFile(fmt::format("tmp/map_render{}{}.png", it.x, it.y));
+    REQUIRE(worked);
+#endif
+  }
+}