diff --git a/builder.cpp b/builder.cpp
index 660029a..214929b 100644
--- a/builder.cpp
+++ b/builder.cpp
@@ -1,5 +1,4 @@
 #include "builder.hpp"
-#include "dbc.hpp"
 #include <chrono>                     // for milliseconds
 #include <fmt/core.h>
 #include <fstream>
@@ -15,6 +14,7 @@
 #include <fstream>
 #include <future>
 #include <mutex>
+#include "dbc.hpp"
 
 using std::string;
 using namespace fmt;
diff --git a/dbc.cpp b/dbc.cpp
new file mode 100644
index 0000000..c25d32a
--- /dev/null
+++ b/dbc.cpp
@@ -0,0 +1,40 @@
+#include "dbc.hpp"
+
+void dbc::log(const string &message) {
+  fmt::print("{}\n", message);
+}
+
+void dbc::sentinel(const string &message) {
+  string err = fmt::format("[SENTINEL!] {}\n", message);
+  throw dbc::SentinelError{err};
+}
+
+void dbc::pre(const string &message, bool test) {
+  if(!test) {
+    string err = fmt::format("[PRE!] {}\n", message);
+    throw dbc::PreCondError{err};
+  }
+}
+
+void dbc::pre(const string &message, std::function<bool()> tester) {
+  dbc::pre(message, tester());
+}
+
+void dbc::post(const string &message, bool test) {
+  if(!test) {
+    string err = fmt::format("[POST!] {}\n", message);
+    throw dbc::PostCondError{err};
+  }
+}
+
+void dbc::post(const string &message, std::function<bool()> tester) {
+  dbc::post(message, tester());
+}
+
+void dbc::check(bool test, const string &message) {
+  if(!test) {
+    string err = fmt::format("[CHECK!] {}\n", message);
+    fmt::println("{}", err);
+    throw dbc::CheckError{err};
+  }
+}
diff --git a/dbc.hpp b/dbc.hpp
index cc4d71c..919d729 100644
--- a/dbc.hpp
+++ b/dbc.hpp
@@ -15,39 +15,15 @@ namespace dbc {
   };
 
   class CheckError : public Error {};
-
   class SentinelError : public Error {};
   class PreCondError : public Error {};
   class PostCondError : public Error {};
 
-  void log(const string &message) {
-    fmt::print("{}\n", message);
-  }
-
-  void sentinel(const string &message) {
-    string err = fmt::format("[SENTINEL!] {}\n", message);
-    throw SentinelError{err};
-  }
-
-  void pre(const string &message, std::function<bool()> tester) {
-    if(!tester()) {
-      string err = fmt::format("[PRE!] {}\n", message);
-      throw PreCondError{err};
-    }
-  }
-
-  void post(const string &message, std::function<bool()> tester) {
-    if(!tester()) {
-      string err = fmt::format("[POST!] {}\n", message);
-      throw PostCondError{err};
-    }
-  }
-
-  void check(bool test, const string &message) {
-    if(!test) {
-      string err = fmt::format("[CHECK!] {}\n", message);
-      fmt::println("{}", err);
-      throw CheckError{err};
-    }
-  }
+  void log(const string &message);
+  void sentinel(const string &message);
+  void pre(const string &message, bool test);
+  void pre(const string &message, std::function<bool()> tester);
+  void post(const string &message, bool test);
+  void post(const string &message, std::function<bool()> tester);
+  void check(bool test, const string &message);
 }
diff --git a/game_engine.cpp b/game_engine.cpp
index 7589cd8..3bf573b 100644
--- a/game_engine.cpp
+++ b/game_engine.cpp
@@ -5,6 +5,7 @@
 #include <fmt/color.h>
 #include "game_engine.hpp"
 #include <cassert>
+#include "dbc.hpp"
 
 const auto ERROR = fmt::emphasis::bold | fg(fmt::color::red);
 
diff --git a/meson.build b/meson.build
index aa39278..01ecd57 100644
--- a/meson.build
+++ b/meson.build
@@ -29,6 +29,7 @@ subdir('scratchpad')
 
 executable('escape_turings_tarpit',
   ['game_engine.cpp',
+    'dbc.cpp',
     'gui.cpp',
     'watcher.cpp',
     'builder.cpp',
@@ -37,9 +38,11 @@ executable('escape_turings_tarpit',
   dependencies: dependencies)
 
 runtests = executable('runtests', [
+  'dbc.cpp',
   'game_engine.cpp',
   'tests/game_engine.cpp',
   'tests/fsm.cpp',
+  'tests/dbc.cpp',
   ],
   dependencies: dependencies + [catch2])
 
diff --git a/sfmlbackend.cpp b/sfmlbackend.cpp
index 64bc203..5c2c0f9 100644
--- a/sfmlbackend.cpp
+++ b/sfmlbackend.cpp
@@ -162,6 +162,13 @@ SFMLBackend::SFMLBackend(GameEngine &g) : window(sf::VideoMode(X_DIM, Y_DIM), "T
 
 }
 
+/*
+ * This makes my sould hurt. Make it stop.
+ *
+ * TODO: Make this more efficient, and don't display
+ * more than 10 or so errors since more than that is
+ * not very useful.
+ */
 void SFMLBackend::update_log(std::vector<string> &lines) {
   log.clear();
   for(string &line : lines) {
diff --git a/status.txt b/status.txt
index bd2b672..ab37297 100644
--- a/status.txt
+++ b/status.txt
@@ -1,14 +1,14 @@
 * Using that to redesign the starter UI.
 
 BUGS:
-* BUG: Log doesn't scroll.
 * BUG: lots of errors crash it
 * BUG: doesn't play you_died sound.
 
 TODO:
 * Rewrite dbc.hpp to actually work.
-* Use parameter pack in FSM template
+
 * Add a timer to the game engine so you can set a kind of pomodoro timer and if you don't meet the goal it costs you.
+
 * Track the deaths.
 
 https://en.cppreference.com/w/cpp/language/parameter_pack
diff --git a/tests/dbc.cpp b/tests/dbc.cpp
new file mode 100644
index 0000000..fa45b86
--- /dev/null
+++ b/tests/dbc.cpp
@@ -0,0 +1,39 @@
+#include <catch2/catch_test_macros.hpp>
+#include "dbc.hpp"
+
+using namespace dbc;
+
+TEST_CASE("basic feature tests", "[utils]") {
+  log("Logging a message.");
+
+  try {
+    sentinel("This shouldn't happen.");
+  } catch(SentinelError) {
+    log("Sentinel happened.");
+  }
+
+  pre("confirm positive cases work", 1 == 1);
+  pre("confirm positive lambda", [&]{ return 1 == 1;});
+  post("confirm positive post", 1 == 1);
+  post("confirm postitive post with lamdba", [&]{ return 1 == 1;});
+
+  check(1 == 1, "one equals 1");
+
+  try {
+    check(1 == 2, "this should fail");
+  } catch(CheckError err) {
+    log("check fail worked");
+  }
+
+  try {
+    pre("failing pre", 1 == 3);
+  } catch(PreCondError err) {
+    log("pre fail worked");
+  }
+
+  try {
+    post("failing post", 1 == 4);
+  } catch(PostCondError err) {
+    log("post faile worked");
+  }
+}