Crate tor_rtmock

Support for mocking with tor-rtcompat asynchronous runtimes.

Overview

The tor-rtcompat crate defines a Runtime trait that represents most of the common functionality of . This crate provides mock implementations that override a Runtime, in whole or in part, for testing purposes.

This crate is part of Arti, a project to implement Tor in Rust. It is used to write tests for higher-level crates in Arti that rely on asynchronous runtimes.

This crate should only be used for writing tests.

Currently, we support mocking the passage of time (via MockSleepRuntime), and impersonating the internet (via MockNetRuntime).

Examples

Suppose you’ve written a function that relies on making a connection to the network and possibly timing out:

use tor_rtcompat::{Runtime,SleepProviderExt};
use std::{net::SocketAddr, io::Result, time::Duration, io::Error};
use futures::io::AsyncWriteExt;

async fn say_hi(runtime: impl Runtime, addr: &SocketAddr) -> Result<()> {
   let delay = Duration::new(5,0);
   runtime.timeout(delay, async {
      let mut conn = runtime.connect(addr).await?;
      conn.write_all(b"Hello world!\r\n").await?;
      conn.close().await?;
      Ok::<_,Error>(())
   }).await??;
   Ok(())
}

But how should you test this function?

You might try connecting to a well-known website to test the connection case, and to a well-known black hole to test the timeout case… but that’s a bit undesirable. Your tests might be running in a container with no internet access; and even if they aren’t, it isn’t so great for your tests to rely on the actual state of the internet. Similarly, if you make your timeout too long, your tests might block for a long time; but if your timeout is too short, the tests might fail on a slow machine or on a slow network.

Or, you could solve both of these problems by using tor-rtmock to replace the internet and the passage of time. (Here we’re only replacing the internet.)

use tor_rtmock::{MockSleepRuntime,MockNetRuntime,net::MockNetwork};
use tor_rtcompat::{TcpProvider,TcpListener};
use futures::io::AsyncReadExt;

tor_rtcompat::test_with_all_runtimes!(|rt| async move {

   let addr1 = "198.51.100.7".parse().unwrap();
   let addr2 = "198.51.100.99".parse().unwrap();
   let sockaddr = "198.51.100.99:101".parse().unwrap();

   // Make a runtime that pretends that we are at the first address...
   let fake_internet = MockNetwork::new();
   let rt1 = fake_internet.builder().add_address(addr1).runtime(rt.clone());
   // ...and one that pretends we're listening at the second address.
   let rt2 = fake_internet.builder().add_address(addr2).runtime(rt);
   let listener = rt2.listen(&sockaddr).await.unwrap();

   // Now we can test our function!
   let (result1,output) = futures::join!(
          say_hi(rt1, &sockaddr),
          async {
              let (mut conn,addr) = listener.accept().await.unwrap();
              assert_eq!(addr.ip(), addr1);
              let mut output = Vec::new();
              conn.read_to_end(&mut output).await.unwrap();
              output
          });

   assert!(result1.is_ok());
   assert_eq!(&output[..], b"Hello world!\r\n");
});

(TODO: Add an example for the timeout case.)

Modules

io

Mocking helpers for testing with futures::io types.

net

Implements a simple mock network for testing purposes.

time

Functionality for simulating the passage of time in unit tests.

Structs

MockNetRuntime

A wrapper Runtime that overrides the SleepProvider trait for the underlying runtime.

MockSleepRuntime

A wrapper Runtime that overrides the SleepProvider trait for the underlying runtime.