tests: Add basic unit tests for fp-context

Link the tests with the private library using an utils library that will
be useful to share other tests functions

tests/test-utils.h

@@ -0,0 +1,23 @@
+/*
+ * Unit tests for libfprint
+ * Copyright (C) 2019 Marco Trevisan <marco.trevisan@canonical.com>
+ *
+ * This library 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; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <glib.h>
+
+void fpt_setup_virtual_device_environment (void);
+void fpt_teardown_virtual_device_environment (void);