signal: Split up all integration tests to run in their own process

* Cargo runs each integration-style-test in its own process. Since the
tests use global data structures specific to the process, we should run
them in an isolated manner to avoid having cross-test interactions
* Fixes alexcrichton/tokio-signal#39

tests/multi_loop.rs

@@ -0,0 +1,47 @@
+#![cfg(unix)]
+
+extern crate futures;
+extern crate libc;
+extern crate tokio;
+extern crate tokio_core;
+extern crate tokio_signal;
+
+use std::sync::mpsc::channel;
+use std::thread;
+
+use futures::stream::Stream;
+use tokio_core::reactor::Core;
+use tokio_signal::unix::Signal;
+
+#[test]
+fn multi_loop() {
+    // An "ordinary" (non-future) channel
+    let (sender, receiver) = channel();
+    // Run multiple times, to make sure there are no race conditions
+    for _ in 0..10 {
+        // Run multiple event loops, each one in its own thread
+        let threads: Vec<_> = (0..4)
+            .map(|_| {
+                let sender = sender.clone();
+                thread::spawn(move || {
+                    let mut lp = Core::new().unwrap();
+                    let signal = lp.run(Signal::new(libc::SIGHUP)).unwrap();
+                    sender.send(()).unwrap();
+                    lp.run(signal.into_future()).ok().unwrap();
+                })
+            })
+            .collect();
+        // Wait for them to declare they're ready
+        for &_ in threads.iter() {
+            receiver.recv().unwrap();
+        }
+        // Send a signal
+        unsafe {
+            assert_eq!(libc::kill(libc::getpid(), libc::SIGHUP), 0);
+        }
+        // Make sure the threads terminated correctly
+        for t in threads {
+            t.join().unwrap();
+        }
+    }
+}