@Test
    void httpsRequestToPlainTextEndpoint() throws Exception {
        final WebClient client = WebClient.builder(SessionProtocol.HTTPS, server.httpEndpoint())
                                          .factory(ClientFactory.insecure()).build();
        final Throwable throwable = catchThrowable(() -> client.get("/hello/world").aggregate().get());
        assertThat(Exceptions.peel(throwable))
                .isInstanceOf(UnprocessedRequestException.class)
                .hasCauseInstanceOf(SSLException.class);
    }
User-agent header should be overridden by ClientOption.HTTP_HEADER
core/src/test/java/com/linecorp/armeria/client/HttpClientIntegrationTest.java