response = new SampleResult();
response.setResponseData(html.getBytes());
URLRewritingModifier mod = new URLRewritingModifier();
mod.setArgumentName("session_id");
HTTPSampler sampler = createSampler();
sampler.addArgument("session_id", "adfasdfdsafasdfasd");
context.setCurrentSampler(sampler);
context.setPreviousResult(response);
mod.process();
Arguments args = sampler.getArguments();
assertEquals("jfdkjdkf jddkfdfjkdjfdf\"", ((Argument) args.getArguments().get(0).getObjectValue()).getValue());