diff --git a/CMakeLists.txt b/CMakeLists.txt
index 88e55dc..613d981 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,10 +5,23 @@ set(PROJECT_NAME dinkyecs_sandbox)
 project(${PROJECT_NAME})
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
-file(GLOB PROJECT_SRC *.cpp *.hpp *.h)
-
 find_package(nlohmann_json)
 find_package(fmt)
 
-add_executable(${PROJECT_NAME} ${PROJECT_SRC})
-target_link_libraries(${PROJECT_NAME} nlohmann_json::nlohmann_json fmt::fmt)
+add_library(dinkyecs STATIC dbc.hpp dbc.cpp dinkyecs.hpp)
+target_link_libraries(dinkyecs ${PROJECT_DEPS} nlohmann_json::nlohmann_json fmt::fmt)
+
+set(PROJECT_DEPS dinkyecs)
+
+add_executable(${PROJECT_NAME} main.cpp)
+target_link_libraries(${PROJECT_NAME} ${PROJECT_DEPS})
+
+#######################################################
+find_package(Catch2 REQUIRED)
+file(GLOB TEST_SRC ./tests/*.cpp ./tests/*.hpp ./tests/*.h) 
+add_executable(tests ${TEST_SRC})
+target_link_libraries(tests PRIVATE Catch2::Catch2WithMain ${PROJECT_DEPS})
+
+include(CTest)
+include(Catch)
+catch_discover_tests(tests)
diff --git a/conanfile.txt b/conanfile.txt
index 1249efb..6c2ad01 100644
--- a/conanfile.txt
+++ b/conanfile.txt
@@ -1,5 +1,6 @@
 [requires]
 nlohmann_json/3.11.3
+catch2/3.8.0
 fmt/11.1.3
 
 [generators]
diff --git a/main.cpp b/main.cpp
index c62f671..954eeb4 100644
--- a/main.cpp
+++ b/main.cpp
@@ -90,9 +90,13 @@ int main()
     configure(world, test);
 
     Position &pos = world.get<Position>(test);
+    Position &pos2 = world.get<Position>(test);
     REQUIRE(pos.location.x == 10);
     REQUIRE(pos.location.y == 20);
 
+    REQUIRE(pos2.location.x == 10);
+    REQUIRE(pos2.location.y == 20);
+    
     Velocity &vel = world.get<Velocity>(test);
     REQUIRE(vel.x == 1);
     REQUIRE(vel.y == 2);
diff --git a/tests/dinkyecs.cpp b/tests/dinkyecs.cpp
new file mode 100644
index 0000000..1813434
--- /dev/null
+++ b/tests/dinkyecs.cpp
@@ -0,0 +1,247 @@
+#define CATCH_CONFIG_MAIN
+#include <catch2/catch_all.hpp>
+#include <catch2/catch_test_macros.hpp>
+#include "../dinkyecs.hpp"
+#include <iostream>
+#include <fmt/core.h>
+
+using namespace fmt;
+using DinkyECS::Entity;
+using std::string;
+
+struct Point {
+  size_t x;
+  size_t y;
+};
+
+struct Player {
+  string name;
+  Entity eid;
+};
+
+struct Position {
+  Point location;
+};
+
+struct Motion {
+  int dx;
+  int dy;
+  bool random=false;
+};
+
+struct Velocity {
+  double x, y;
+};
+
+struct Gravity {
+  double level;
+};
+
+struct DaGUI {
+  int event;
+};
+
+/*
+ * Using a function catches instances where I'm not copying
+ * the data into the world.
+ */
+void configure(DinkyECS::World &world, Entity &test) {
+  println("---Configuring the base system.");
+  Entity test2 = world.entity();
+
+  world.set<Position>(test, {10,20});
+  world.set<Velocity>(test, {1,2});
+
+  world.set<Position>(test2, {1,1});
+  world.set<Velocity>(test2, {9,19});
+
+  println("---- Setting up the player as a fact in the system.");
+
+  auto player_eid = world.entity();
+  Player player_info{"Zed", player_eid};
+  // just set some player info as a fact with the entity id
+  world.set_the<Player>(player_info);
+
+  world.set<Velocity>(player_eid, {0,0});
+  world.set<Position>(player_eid, {0,0});
+
+  auto enemy = world.entity();
+  world.set<Velocity>(enemy, {0,0});
+  world.set<Position>(enemy, {0,0});
+
+  println("--- Creating facts (singletons)");
+  world.set_the<Gravity>({0.9});
+}
+
+TEST_CASE("confirm ECS system works", "[ecs]") {
+  DinkyECS::World world;
+  Entity test = world.entity();
+
+  configure(world, test);
+
+  Position &pos = world.get<Position>(test);
+  REQUIRE(pos.location.x == 10);
+  REQUIRE(pos.location.y == 20);
+
+  Velocity &vel = world.get<Velocity>(test);
+  REQUIRE(vel.x == 1);
+  REQUIRE(vel.y == 2);
+
+  world.query<Position>([](const auto &ent, auto &pos) {
+      REQUIRE(ent > 0);
+      REQUIRE(pos.location.x >= 0);
+      REQUIRE(pos.location.y >= 0);
+  });
+
+  world.query<Velocity>([](const auto &ent, auto &vel) {
+      REQUIRE(ent > 0);
+      REQUIRE(vel.x >= 0);
+      REQUIRE(vel.y >= 0);
+  });
+
+  println("--- Manually get the velocity in position system:");
+  world.query<Position>([&](const auto &ent, auto &pos) {
+      Velocity &vel = world.get<Velocity>(ent);
+
+      REQUIRE(ent > 0);
+      REQUIRE(pos.location.x >= 0);
+      REQUIRE(pos.location.y >= 0);
+      REQUIRE(ent > 0);
+      REQUIRE(vel.x >= 0);
+      REQUIRE(vel.y >= 0);
+  });
+
+  println("--- Query only entities with Position and Velocity:");
+  world.query<Position, Velocity>([&](const auto &ent, auto &pos, auto &vel) {
+      Gravity &grav = world.get_the<Gravity>();
+      REQUIRE(grav.level <= 1.0f);
+      REQUIRE(grav.level > 0.5f);
+      REQUIRE(ent > 0);
+      REQUIRE(pos.location.x >= 0);
+      REQUIRE(pos.location.y >= 0);
+      REQUIRE(ent > 0);
+      REQUIRE(vel.x >= 0);
+      REQUIRE(vel.y >= 0);
+  });
+
+  // now remove Velocity
+  REQUIRE(world.has<Velocity>(test));
+  world.remove<Velocity>(test);
+  REQUIRE_THROWS(world.get<Velocity>(test));
+  REQUIRE(!world.has<Velocity>(test));
+
+  println("--- After remove test, should only result in test2:");
+  world.query<Position, Velocity>([&](const auto &ent, auto &pos, auto &vel) {
+      auto &in_position = world.get<Position>(ent);
+      auto &in_velocity = world.get<Velocity>(ent);
+      REQUIRE(pos.location.x >= 0);
+      REQUIRE(pos.location.y >= 0);
+      REQUIRE(in_position.location.x == pos.location.x);
+      REQUIRE(in_position.location.y == pos.location.y);
+      REQUIRE(in_velocity.x == vel.x);
+      REQUIRE(in_velocity.y == vel.y);
+  });
+}
+
+enum GUIEvent {
+  HIT, MISS
+};
+
+TEST_CASE("confirm that the event system works", "[ecs]") {
+  DinkyECS::World world;
+  DinkyECS::Entity player = world.entity();
+
+  world.send<GUIEvent>(GUIEvent::HIT, player, string{"hello"});
+
+  bool ready = world.has_event<GUIEvent>();
+  REQUIRE(ready == true);
+
+  auto [event, entity, data] = world.recv<GUIEvent>();
+  REQUIRE(event == GUIEvent::HIT);
+  REQUIRE(entity == player);
+  auto &str_data = std::any_cast<string&>(data);
+  REQUIRE(string{"hello"} == str_data);
+
+  ready = world.has_event<GUIEvent>();
+  REQUIRE(ready == false);
+}
+
+
+TEST_CASE("confirm copying and constants", "[ecs-constants]") {
+  DinkyECS::World world1;
+
+  Player player_info{"Zed", world1.entity()};
+  world1.set_the<Player>(player_info);
+
+  world1.set<Position>(player_info.eid, {10,10});
+  world1.make_constant(player_info.eid);
+
+  DinkyECS::World world2;
+  world1.clone_into(world2);
+
+  auto &test1 = world1.get<Position>(player_info.eid);
+  auto &test2 = world2.get<Position>(player_info.eid);
+
+  REQUIRE(test2.location.x == test1.location.x);
+  REQUIRE(test2.location.y == test1.location.y);
+
+  // check for accidental reference
+  test1.location.x = 100;
+  REQUIRE(test2.location.x != test1.location.x);
+
+  // test the facts copy over
+  auto &player2 = world2.get_the<Player>();
+  REQUIRE(player2.eid == player_info.eid);
+}
+
+
+TEST_CASE("test serialization with nlohmann::json", "[ecs-serialize]") {
+  /*
+  DinkyECS::ComponentMap component_map;
+  DinkyECS::Component<Position>(component_map);
+  DinkyECS::Component<Velocity>(component_map);
+  DinkyECS::Component<Motion>(component_map);
+  DinkyECS::Component<Gravity>(component_map);
+  DinkyECS::Component<DaGUI>(component_map);
+
+  auto data = R"(
+    [
+        {
+            "_type": "Position",
+            "location": {
+              "x": 10,
+              "y": 5
+            }
+        },
+        {
+            "_type": "Motion",
+            "dx": 0,
+            "dy": 1
+        },
+        {
+            "_type": "Velocity",
+            "x": 0.1,
+            "y": 10.2
+        }
+    ]
+  )"_json;
+
+  DinkyECS::World world;
+  DinkyECS::Entity ent1 = world.entity();
+  DinkyECS::Entity ent2 = world.entity();
+
+  DinkyECS::configure(component_map, world, ent1, data);
+  DinkyECS::configure(component_map, world, ent2, data);
+
+  world.query<Position, Motion>([&](const auto ent, auto &pos, auto &motion) {
+      fmt::println("entity: {}; position={},{} and motion={},{} motion.random={}",
+          ent, pos.location.x, pos.location.y,
+          motion.dx, motion.dy, motion.random);
+      REQUIRE(pos.location.x == 10);
+      REQUIRE(pos.location.y == 5);
+      REQUIRE(motion.dx == 0);
+      REQUIRE(motion.dy == 1);
+      REQUIRE(motion.random == false);
+  });
+  */
+}