diff --git a/test/string.cpp b/test/string.cpp
index 6f663813..2bd68ba8 100644
--- a/test/string.cpp
+++ b/test/string.cpp
@@ -5,11 +5,11 @@
 
 #include <vector>
 
-int
-main (int, char**)
-{
-    cruft::TAP::logger tap;
 
+///////////////////////////////////////////////////////////////////////////////
+void
+test_tokeniser (cruft::TAP::logger &tap)
+{
     // the string_literal prefix is required to (easily) construct a string
     // with an internal null character.
     using namespace std::literals::string_literals;
@@ -33,6 +33,16 @@ main (int, char**)
     for (auto [tok, expected]: cruft::zip (cruft::tokeniser (src, ','), TESTS)) {
         tap.expect (equal (tok, expected.value), "%s", expected.message);
     }
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+int
+main (int, char**)
+{
+    cruft::TAP::logger tap;
+
+    test_tokeniser (tap);
 
     return tap.status ();
 }
\ No newline at end of file