public static Builder builder(Map<String, String> properties) {
    return new Builder(properties);
  }
@Test
  public void testProxyServerWithNullHostname() {
    assertThatThrownBy(
            () -> HTTPClient.builder(ImmutableMap.of()).uri(URI).withProxy(null, 1070).build())
        .isInstanceOf(NullPointerException.class)
        .hasMessage("Invalid hostname for http client proxy: null");
  }