@Test
public void testFilenameMeansMultiSwitch() throws Throwable {

  Configuration conf = new Configuration();
  conf.set(ScriptBasedMapping.SCRIPT_FILENAME_KEY, "any-filename");
  ScriptBasedMapping mapping = createMapping(conf);
  assertFalse("Expected to be multi switch", mapping.isSingleSwitch());
  mapping.setConf(new Configuration());
  assertTrue("Expected to be single switch", mapping.isSingleSwitch());
}