diff --git a/lib/core.fs b/lib/core.fs
index 399f44f..66821a8 100644
--- a/lib/core.fs
+++ b/lib/core.fs
@@ -9,3 +9,13 @@ defined? roll [unless]
         dup 0<= if drop else swap >r 1- recurse r> swap then
     ;
 [then]
+
+
+\ Ignore test codes. lib/tester.fs will redefine this when
+\ running tests.
+: T{
+    begin
+        word throw
+        s" }T" streq if exit then
+    again
+;
diff --git a/test/tester.fs b/lib/tester.fs
similarity index 100%
rename from test/tester.fs
rename to lib/tester.fs
diff --git a/runtests.fs b/runtests.fs
index d4fcf83..b440abb 100644
--- a/runtests.fs
+++ b/runtests.fs
@@ -6,7 +6,8 @@
 
 ." Running PlanckForth test programs" cr
 
-include test/tester.fs
+include lib/tester.fs
+
 include test/core.fs
 include test/utilities.fs
 include test/errorreport.fs