birdtest: in unit tests, bt_assert_bug() asserts that given function will produce bug with given message

lib/fail_test.c

@@ -0,0 +1,22 @@
+#include "test/birdtest.h"
+
+void
+just_bug_fce(void)
+{
+  bug("bug message");
+}
+
+static int
+t_check_bug(void)
+{
+  return bt_assert_bug(just_bug_fce, "bug message");
+}
+
+int
+main(int argc, char *argv[])
+{
+  bt_init(argc, argv);
+  bt_test_suite(t_check_bug,	"bug fce");
+
+  return bt_exit_value();
+}