private Response conditionalGet(String path, String etag) throws IOException {
    return client.newCall(new Request.Builder()
      .url(url(server, path))
      .header("If-None-Match", etag)
      .build()).execute();
  }
index.html is served separately. This tests other content is also loaded from the classpath.
zipkin-server/src/test/java/zipkin2/server/internal/ui/ITZipkinUiConfiguration.java