@Test(expected = IOException.class)
public void testReadInFileWithoutExtension() throws MalformedURLException, IOException {

  final File testFile = new File("temp" + File.separator + "fdkajdl3eaf");
  final ImageFileSource fileSource = new ImageFileSource(osf, origin -> null, testFile);
  fileSource.initialize();
  fail("initialize() should have thrown an IOException");
}