tests: add a test for bdd_dict::assert_emptiness()

This improves the coverage for bdd_dict::assert_emptiness() and
bdd_dict::dump().

* tests/core/bdddict.cc, tests/core/bdddict.test: New files.
* tests/Makefile.am, tests/core/.gitignore: Adjust.

tests/core/bdddict.test

@@ -0,0 +1,29 @@
+#!/bin/sh
+# -*- coding: utf-8 -*-
+# Copyright (C) 2017 Laboratoire de Recherche et Développement de
+# l'Epita (LRDE).
+#
+# This file is part of Spot, a model checking library.
+#
+# Spot 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 3 of the License, or
+# (at your option) any later version.
+#
+# Spot 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, see <http://www.gnu.org/licenses/>.
+
+. ./defs
+set -e
+
+# Exercise bdd_dict::assert_emptiness()
+../bdddict 2>stderr && exit 1
+grep 'some maps are not empty' stderr
+grep 'Var\[p0\] x2' stderr
+grep 'Var\[p1\] x2' stderr
+grep 'Var\[p2\] x2' stderr