@Test
public void testNoDonors() throws Exception {

  final File donors = temporaryFolder.newFolder();
  final File references = temporaryFolder.newFolder();
  final String outputDir = new File(temporaryFolder.getRoot(), "output").getAbsolutePath();
  assertTrue(donors.delete());
  try {
    GenerateAndRunShaders.mainHelper(
          new String[] {
              references.getAbsolutePath(),
              donors.getAbsolutePath(),
              outputDir,
              "dummy_server",
              "dummy_worker"
          }
    );
    throw new RuntimeException("Exception expected.");
  } catch (IllegalArgumentException exception) {
    assertEquals("Donors directory does not exist.", exception.getMessage());
  }
}