public ClassicHttpResponse execute(final ClassicHttpRequest request) throws IOException, HttpException {
        return impl.execute(
                ClassicRequestBuilder.copy(request).build(),
                new ExecChain.Scope("test", route, request, mockExecRuntime, context),
                mockExecChain);
    }
A suite of acceptance tests for compliance with RFC5861, which
describes the stale-if-error and stale-while-revalidate
Cache-Control extensions.
httpclient5-cache/src/test/java/org/apache/hc/client5/http/impl/cache/TestRFC5861Compliance.java