private static void testHeaderOverridableByClientOption(String path, AsciiString headerName,
                                                            String headerValue) throws Exception {
        final BlockingWebClient client = WebClient.builder(server.httpUri())
                                                  .setHeader(headerName, headerValue)
                                                  .build()
                                                  .blocking();

        final AggregatedHttpResponse response = client.get(path);

        assertThat(response.contentUtf8()).isEqualTo(headerValue);
    }
User-agent header should be overridden by ClientOption.HTTP_HEADER
core/src/test/java/com/linecorp/armeria/client/HttpClientIntegrationTest.java