@SuppressWarnings({"unchecked"})
    public String render(Renderer renderer, DataList data) throws InterruptedException, IOException {
        TestContentChannel contentChannel = new TestContentChannel();

        Execution execution = Execution.createRoot(new NoopProcessor(), 0, null);

        final ContentChannelOutputStream stream = new ContentChannelOutputStream(contentChannel);
        CompletableFuture<Boolean> result = renderer.renderResponse(stream, new Response(data), execution, null);

        int waitCounter = 1000;
        while (!result.isDone()) {
            Thread.sleep(60);
            --waitCounter;
            if (waitCounter < 0) {
                throw new IllegalStateException();
            }
        }

        stream.close();
        contentChannel.close(null);

        String str = "";
        for (ByteBuffer buf : contentChannel.getBuffers()) {
            str += Utf8.toString(buf);
        }
        return str;
    }
Validate we get a full response with a malformed response structure.
container-core/src/test/java/com/yahoo/processing/rendering/AsynchronousSectionedRendererTest.java