RegistryEndpointProvider<Optional<URL>> initializer() {
    return new Initializer();
  }
@Test
  public void testInitializer_handleResponse_accepted_multipleLocations()
      throws IOException, RegistryException {
    Mockito.when(mockResponse.getStatusCode()).thenReturn(202); // Accepted
    Mockito.when(mockResponse.getHeader("Location"))
        .thenReturn(Arrays.asList("location1", "location2"));
    try {
      testBlobPusher.initializer().handleResponse(mockResponse);
      Assert.fail("Multiple 'Location' headers should be a registry error");

    } catch (RegistryErrorException ex) {
      MatcherAssert.assertThat(
          ex.getMessage(),
          CoreMatchers.containsString("Expected 1 'Location' header, but found 2"));
    }
  }