new file mode 100644
--- /dev/null
+++ b/scripts/testfun/fail.m
@@ -0,0 +1,107 @@
+## -*- texinfo -*-
+## @deftypefn {Function File} {} fail (@var{code},@var{pattern})
+## @deftypefnx {Function File} {} fail (@var{code},'warning',@var{pattern})
+##
+## Return true if @var{code} fails with an error message matching
+## @var{pattern}, otherwise produce an error. Note that @var{code}
+## is a string and if @var{code} runs successfully, the error produced is:
+##
+## @example
+##           expected error but got none  
+## @end example
+##
+## If the code fails with a different error, the message produced is:
+##
+## @example
+##           expected <pattern>
+##           but got <text of actual error>
+## @end example
+##
+## The angle brackets are not part of the output.
+##
+## Called with three arguments, the behavior is similar to 
+## @code{fail(@var{code}, @var{pattern})}, but produces an error if no 
+## warning is given during code execution or if the code fails.
+##
+## @end deftypefn
+
+## This program is public domain
+## Author: Paul Kienzle <pkienzle@users.sf.net>
+
+## PKG_ADD mark_as_command fail
+function ret=fail(code,pattern,warning_pattern)
+  if nargin < 1 || nargin > 3
+    usage("fail(code [, 'warning'] [, pattern])");
+  endif
+
+  ## sort out arguments
+  test_warning =  (nargin > 1 && strcmp(pattern,'warning'));
+  if nargin == 3
+    pattern = warning_pattern;
+  elseif nargin == 1 || (nargin==2 && test_warning)
+    pattern = "";
+  endif
+  if isempty(pattern), pattern = "."; endif  # match any nonempty message
+
+  ## allow assert(fail())
+  if nargout, ret=1; endif  
+
+  ## don't test failure if evalin doesn't exist
+  if !exist('evalin') || !exist('lastwarn'), return; endif
+
+  if test_warning
+    ## perform the warning test
+    lastwarn();  # clear old warnings
+    state = warning("query","quiet"); # make sure warnings are turned on
+    warning("on","quiet");
+    try
+      ## printf("lastwarn before %s: %s\n",code,lastwarn);
+      evalin("caller",sprintf("%s;",code));
+      ## printf("lastwarn after %s: %s\n",code,lastwarn);
+      err = lastwarn;  # retrieve new warnings
+      warning(state.state,"quiet");
+      if isempty(err), 
+        msg = sprintf("expected warning <%s> but got none", pattern); 
+      else
+        err([1:9,end]) = [];  # transform "warning: ...\n" to "..."
+        if !isempty(regexp(err,pattern,"once")), return; end
+        msg = sprintf("expected warning <%s>\nbut got <%s>", pattern,err);
+      endif
+    catch
+      warning(state.state,"quiet");
+      err = lasterr;
+      err([1:7,end]) = [];  # transform "error: ...\n", to "..."
+      msg = sprintf("expected warning <%s> but got error <%s>", pattern, err);
+    end
+      
+  else
+    ## perform the error test
+    try
+      evalin("caller",sprintf("%s;",code));
+      msg = sprintf("expected error <%s> but got none", pattern);
+    catch
+      err=lasterr;
+      if (strcmp(err(1:7),"error:"))
+         err([1:6,end]) = []; # transform "error: ...\n", to "..."
+      endif
+      if !isempty(regexp(err,pattern,"once")), return; end
+      msg = sprintf("expected error <%s>\nbut got <%s>",pattern,err);
+    end
+  endif
+
+  ## if we get here, then code didn't fail or error didn't match
+  error(msg);
+endfunction
+
+%!fail ('[1,2]*[2,3]','nonconformant')
+%!fail ("fail('[1,2]*[2;3]','nonconformant')","expected error <nonconformant> but got none")
+%!fail ("fail('[1,2]*[2,3]','usage:')","expected error <usage:>\nbut got.*nonconformant")
+%!fail ("warning('test warning')",'warning','test warning');
+
+%!# fail ("warning('next test')",'warning','next test');  ## only allowed one warning test?!?
+
+## Comment out the following tests if you don't want to see what
+## errors look like
+% !fail ('a*[2;3]', 'nonconformant')
+% !fail ('a*[2,3]', 'usage:')
+% !fail ("warning('warning failure')", 'warning', 'success')