Be tolerant of zero-page jobs

https://github.com/OpenPrinting/cups-filters/issues/117

test/test_job.cc

@@ -0,0 +1,35 @@
+// This file is part of the brlaser printer driver.
+//
+// Copyright 2020 Peter De Wachter
+//
+// brlaser 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.
+//
+// brlaser 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 brlaser.  If not, see <http://www.gnu.org/licenses/>.
+
+#include "lest.hpp"
+#include "tempfile.h"
+#include "../src/job.h"
+
+const lest::test specification[] = {
+  "An empty job produces no output",
+  [] {
+    tempfile f;
+    {
+      job j(f.file(), "name");
+    }
+    EXPECT(f.data().empty());
+  },
+};
+
+int main() {
+  return lest::run(specification);
+}