diff --git a/gui/Scyther/Scyther.py b/gui/Scyther/Scyther.py
index 7970506..2a735ac 100755
--- a/gui/Scyther/Scyther.py
+++ b/gui/Scyther/Scyther.py
@@ -262,13 +262,6 @@ class Scyther(object):
         if spdl:
             os.remove(fni)
 
-        # Now if there is no output and no errors, weird things might
-        # happen, and we report the command used.
-        if errors == "" and output == "":
-            errors = "Scyther backend did not yield any output, "
-            errors += "returning no errors and no output.\n"
-            errors += "Command: [%s]" % self.cmd
-
         return (output,errors)
 
     def sanitize(self):
diff --git a/gui/test-delta.py b/gui/test-delta.py
new file mode 100755
index 0000000..d2cb25c
--- /dev/null
+++ b/gui/test-delta.py
@@ -0,0 +1,181 @@
+#!/usr/bin/python
+"""
+	Scyther : An automatic verifier for security protocols.
+	Copyright (C) 2007 Cas Cremers
+
+	This program is free software; you can redistribute it and/or
+	modify it under the terms of the GNU General Public License
+	as published by the Free Software Foundation; either version 2
+	of the License, or (at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with this program; if not, write to the Free Software
+	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+"""
+
+
+"""
+
+Example script to show how to perform large-scale tests using the
+Scyther Python API (contained in the Scyther subdirectory)
+
+In this example, we find the differences between two different switch
+settings for a large set of protocols.
+
+The notification triggers if claim lists differ, or when a claim is okay
+in one test but not in the other. Hence, we ignore differences between
+complete/bounded verification.
+
+Author: Cas Cremers
+
+
+Define the strings below.
+
+TEST0 is used for both, TEST1/2 define the difference between
+the tests.
+"""
+#---------------------------------------------------------------------------
+
+TEST0 = ""
+TEST1 = "--max-runs=1"
+TEST2 = "--max-runs=4"
+
+#---------------------------------------------------------------------------
+
+""" Import externals """
+import commands
+
+#---------------------------------------------------------------------------
+
+""" Import scyther components """
+from Scyther import Scyther
+
+#---------------------------------------------------------------------------
+
+def filterProtocol(protocol):
+    """
+    We may want to filter out some protocols.
+    This function allows that. Return True if it is okay (and should be
+    included) or False otherwise.
+    """
+    include = True
+    return include
+
+def simpleRun(args):
+    x = Scyther.Scyther()
+    x.options = args
+    x.verify()
+    return x
+
+def ScytherRes(protocol,args=""):
+    """
+    Run Scyther on a protocol and return a tuple with the
+    resulting object and claim list.
+    """
+    global TEST0
+
+    args = "%s %s %s" % (TEST0, args, protocol)
+    s = simpleRun(args)
+    return (s,s.claims)
+
+
+def findSameClaim(cl,claim):
+    """
+    Find in claim list the claim that corresponds to claim
+    """
+    for claim2 in cl:
+        if claim2.id == claim.id:
+            return claim2
+    return None
+
+
+def ScytherDiff(protocol):
+    """
+    Check whether the two different switch settings yield a different
+    result.
+    """
+    global TEST1, TEST2
+
+    (s1,cl1) = ScytherRes(protocol,TEST1)
+    (s2,cl2) = ScytherRes(protocol,TEST2)
+
+    res = ""
+    if len(cl1) != len(cl2):
+        res += "Different claim lists:\n%s\n%s\n" % (cl1,cl2)
+    else:
+        for claim1 in cl1:
+            claim2 = findSameClaim(cl2,claim1)
+            if claim2 == None:
+                res += "%s not in second test.\n" % (claim1)
+            else:
+                if claim1.okay != claim2.okay:
+                    res += "Different results:\n%s\n%s\n" % (claim1,claim2)
+
+    if res == "":
+        return None
+    else:
+        return res
+
+
+def findProtocols():
+    """
+    Find a list of protocol names
+    """
+
+    cmd = "find -iname '*.spdl'"
+    plist = commands.getoutput(cmd).splitlines()
+    nlist = []
+    for prot in plist:
+        if filterProtocol(prot):
+            nlist.append(prot)
+    return nlist
+
+
+def main():
+    """
+    Simple test case with a few protocols
+    """
+    global TEST0,TEST1,TEST2
+
+    list = findProtocols()
+    print "Performing delta analysis"
+    print 
+    print "String 0 (used for both): '%s'" % TEST0
+    print "String 1: '%s'" % TEST1
+    print "String 2: '%s'" % TEST2
+    print
+    print "After filtering, we are left with the following protocols:", list
+    print
+    maxcount = len(list)
+    count = 1
+    delta = 0
+    for prot in list:
+        perc = (100 * count) / maxcount
+        print "[%i%%] %s: " % (perc,prot),
+        res = ScytherDiff(prot)
+        if res != None:
+            print
+            print "-" * 72
+            print prot
+            print "-" * 72
+            print res
+            delta = delta + 1
+        else:
+            print "No interesting delta found."
+        count = count + 1
+
+    print
+    print "Analysis complete."
+    print "%i out of %i protocols differed [%i%%]." % (delta,maxcount,(100 * delta)/maxcount)
+
+
+if __name__ == '__main__':
+    main()
+
+
+# vim: set ts=4 sw=4 et list lcs=tab\:>-:
diff --git a/gui/mpa.py b/gui/test-mpa.py
similarity index 100%
rename from gui/mpa.py
rename to gui/test-mpa.py