So I'm using the following code in my own HtmlUnitDriver and thought it might be useful for other people as well.

My main use cases are all debugging related like:

• Log every request that is actually executed
• Request manipulation: like re-pointing a minifyed version of resource to a non minifyed version or 'full-of-console-logging' version ;-)
• Request manipulation: changing the request from a POST request to a GET request to test certain CSRF conditions without having to rebuild the main application.

Thought I share this here ... feel free to close if the consent is that it's not needed (since everyone can already do what I'm doing here with a bit more effort)

public class CustomHtmlUnitDriver extends HtmlUnitDriver {

    private List<IHtmlUnitRequestInterceptor> requestInterceptors = new ArrayList<>();

    public CustomHtmlUnitDriver() {
        super(true);

        try (WebConnectionWrapper conWrapper = new WebConnectionWrapper(getWebClient()) {
            @Override
            public WebResponse getResponse(WebRequest request) throws IOException {
                requestInterceptors.forEach(interceptor -> interceptor.onBeforeRequest(request));
                WebResponse response = super.getResponse(request);
                requestInterceptors.forEach(interceptor -> interceptor.onAfterRequest(request, response));
                return response;
            }
        }) {
        } catch (IOException e) {
            throw new RuntimeException("unable to close connectionWrapper", e);
        }
    }

    public void registerRequestInterceptor(IHtmlUnitRequestInterceptor requestInterceptor) {
        requestInterceptors.add(requestInterceptor);
    }

    public static interface IHtmlUnitRequestInterceptor {

        /**
         * Will be called for every request. Response has not being asked for yet.
         */
        void onBeforeRequest(WebRequest webRequest);

        /**
         * Callback after an request.
         */
        void onAfterRequest(WebRequest webRequest, WebResponse response);
    }

}