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

tests/inventory.cpp

@@ -0,0 +1,52 @@
+#include <catch2/catch_test_macros.hpp>
+#include <fmt/core.h>
+#include <string>
+#include "game/inventory.hpp"
+
+using namespace fmt;
+
+TEST_CASE("base test", "[inventory]") {
+  return;
+  inventory::Model inv;
+  DinkyECS::Entity test_ent = 1;
+
+  bool good = inv.add("hand_l", test_ent);
+  inv.invariant();
+  REQUIRE(good);
+
+  auto& slot = inv.get(test_ent);
+  REQUIRE(slot == "hand_l");
+
+  // confirm that we get false when trying to do it again
+  // BUG: this dies
+  good = inv.add("hand_l", test_ent);
+  REQUIRE(!good);
+
+  auto ent = inv.get(slot);
+  REQUIRE(ent == test_ent);
+
+  REQUIRE(inv.has(ent));
+  REQUIRE(inv.has(slot));
+
+  // test base remove
+  inv.remove(ent);
+  REQUIRE(!inv.has(slot));
+  REQUIRE(!inv.has(ent));
+}
+
+TEST_CASE("test swapping items", "[inventory]") {
+  inventory::Model inv;
+  DinkyECS::Entity hand_l_ent = 10;
+  DinkyECS::Entity hand_r_ent = 20;
+
+  inv.add("hand_l", hand_l_ent);
+  inv.add("hand_r", hand_r_ent);
+  REQUIRE(inv.count() == 2);
+
+  inv.swap(hand_l_ent, hand_r_ent);
+
+  REQUIRE(inv.get("hand_l") == hand_r_ent);
+  REQUIRE(inv.get("hand_r") == hand_l_ent);
+
+  REQUIRE(inv.count() == 2);
+}