HTTPSampler sampler = new HTTPSampler();
sampler.setDomain("server.com");
sampler.setPath("index.html");
sampler.setMethod(HTTPSampler.GET);
sampler.setProtocol("http");
sampler.addArgument("session_id", "adfasdfdsafasdfasd");
mod.modifyEntry(sampler, response);
Arguments args = sampler.getArguments();
assertEquals(
"jfdkjdkf%jddkfdfjkdjfdf",
((Argument) args.getArguments().get(0)).getValue());