Extend concretization test to excercise bug in concretize's provider sorting

var/spack/repos/builtin.mock/packages/externalvirtual/package.py

@@ -31,8 +31,10 @@ class Externalvirtual(Package):
 
     version('1.0', '1234567890abcdef1234567890abcdef')
     version('2.0', '234567890abcdef1234567890abcdef1')
+    version('2.1', '34567890abcdef1234567890abcdef12')
+    version('2.2', '4567890abcdef1234567890abcdef123')
 
-    provides('stuff')
+    provides('stuff', when='@1.0:')
 
     def install(self, spec, prefix):
         pass

var/spack/repos/builtin.mock/packages/othervirtual/package.py

+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# 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 terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class Othervirtual(Package):
+    homepage = "http://somewhere.com"
+    url      = "http://somewhere.com/stuff-1.0.tar.gz"
+
+    version('1.0', '67890abcdef1234567890abcdef12345')
+
+    provides('stuff')
+
+    def install(self, spec, prefix):
+        pass