http_replayer is a level of middleware for hyper that replays HTTP server responses. This lets your tests be deterministic, and not have to rely on (or wait for) the network to run your tests. This project is similar to the Ruby project vcr, if you've used something like that before.

You could probably have written this library yourself. It simply maintains a HashMap from (URL, Request) pairs to server responses. If sending the same request to the same server multiple times always produces the same response from the server, then you can use http_replayer.

Here's an example in code:

extern crate hyper;
extern crate http_replayer;
use std::io::Read;
use hyper::Client;
use http_replayer::mock::MockConnector;
fn main() {
    // Create a client.
    //
    // Normally (and in production), you would do this:
    //
    // let mut client = Client::new();
    //
    // But with http_replayer (in your tests), you write:
    let mut client = Client::with_connector(MockConnector::new("testing")); // the "testing" is explained below
    // Creating an outgoing request.
    //
    // The first time you run this, Hyper will actually send out a request to
    // the internet, but every time thereafter a locally saved response will be
    // returned instead.
    let mut res = client.get("https://www.example.com/")
        // let 'er go!
        .send().unwrap();
    // Read the Response.
    let mut body = String::new();
    res.read_to_string(&mut body).unwrap();
    println!("Response: {}", body);
}

A MockConnector plugs into hyper's NetworkConnector interface to do its' magic. MockConnector#new accepts a context: &str as argument -- using unique contexts allows you to use multiple http_replayer sessions concurrently.

In the example above, because we passed "testing" as the context, the HTTP request and response was saved in a file called ./fixtures/http_replayer/testing.json, which you may want to check into version control. All of http_replayer's saved state is stored in this file, so to completely reset http_replayer, you simply need to delete this file.

http_replayer is very new right now. You should not be using it in production.