diff --git a/lutro.c b/lutro.c
index ad0626d..173e387 100644
--- a/lutro.c
+++ b/lutro.c
@@ -204,9 +204,41 @@ static void init_lutro_global_table(lua_State *L)
    lua_pop(L, 1);
 }
 
+// reveals which configuration options were used to compile lutro.
+static void init_config(lua_State *L)
+{   
+   player_checked_stack_begin(L);
+
+   luax_reqglobal(L, "lutro");
+   lua_newtable(L);
+
+   char buf[128];
+
+   #define STR(a) #a
+   #define CAPABILITY(cap)                           \
+      snprintf(buf, sizeof(buf), "%s", #cap);        \
+      lua_pushboolean(L, (buf[0] && strtold(buf, NULL) != 0)); \
+      lua_setfield(L, -2, #cap)
+
+   CAPABILITY(HAVE_COMPOSITION);
+   CAPABILITY(HAVE_TRANSFORM);
+   CAPABILITY(HAVE_INOTIFY);
+   CAPABILITY(HAVE_JIT);
+   CAPABILITY(HAVE_LUASOCKET);
+
+   #undef STR
+   #undef CAPABILITY
+
+   lua_setfield(L, -2, "featureflags");
+   lua_pop(L, 1);
+
+   (void)player_checked_stack_end(L,0);
+}
 
 static int lutro_core_preload(lua_State *L)
 {
+   init_config(L);
+
    return 1;
 }
 
@@ -229,11 +261,13 @@ static void init_settings(lua_State *L)
 
 void lutro_newlib_x(lua_State* L, luaL_Reg const* funcs, char const* fieldname, int numfuncs)
 {
+   player_checked_stack_begin(L);
    luax_reqglobal(L, "lutro");
    lua_createtable(L, 0, numfuncs);
    luaL_setfuncs(L, funcs, 0);
    lua_setfield(L, -2, fieldname);
    lua_pop(L, 1);
+   player_checked_stack_end(L,0);
 }
 
 void lutro_init()
diff --git a/test/main.lua b/test/main.lua
index 613af7d..992767f 100644
--- a/test/main.lua
+++ b/test/main.lua
@@ -1,5 +1,6 @@
 -- Lutro Tester
 local availableStates = {
+	"config/print",
 	"graphics/print",
 	"unit/tests",
 	"joystick/isDown",
diff --git a/test/unit/modules/filesystem.lua b/test/unit/modules/filesystem.lua
index 59217c2..20ca449 100644
--- a/test/unit/modules/filesystem.lua
+++ b/test/unit/modules/filesystem.lua
@@ -24,7 +24,7 @@ function lutro.filesystem.getUserDirectoryTest()
     -- Other aspects of UserDirectory are platform specific and non-trivial to calculate and there
     -- isn't much value to trying to replicate it here.
     local userDir = lutro.filesystem.getUserDirectory()
-    local userDirFixed = getUserDir
+    local userDirFixed = userDir
     if userDirFixed:sub(-1) ~= '/' then
         userDirFixed = userDirFixed .. '/'
     end
diff --git a/test/unit/tests.lua b/test/unit/tests.lua
index 0d199c7..b794afe 100644
--- a/test/unit/tests.lua
+++ b/test/unit/tests.lua
@@ -7,6 +7,7 @@ unit = require 'luaunit'
 -- Runs all tests.
 function runTests()
 	local moduleTests = {
+		require 'modules/featureflags',
 		require 'modules/filesystem',
 		require 'modules/graphics',
 		require 'modules/keyboard',