gcc/testsuite/algol68/execute/plusab-string-1.a68

# { dg-options "-fstropping=upper" }  #
BEGIN STRING foo := "";
      foo +:= "foo";
      ASSERT (LWB foo = 1 AND UPB foo = 3 AND foo = "foo");
      foo PLUSAB "bar";
      ASSERT (LWB foo = 1 AND UPB foo = 6 AND foo = "foobar")
END