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