Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/tests/buffered.rs

@@ -0,0 +1,50 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi does not support bind()
+
+use tokio::net::TcpListener;
+use tokio_test::assert_ok;
+
+use std::io::prelude::*;
+use std::net::TcpStream;
+use std::thread;
+
+#[tokio::test]
+async fn echo_server() {
+    const N: usize = 1024;
+
+    let srv = assert_ok!(TcpListener::bind("127.0.0.1:0").await);
+    let addr = assert_ok!(srv.local_addr());
+
+    let msg = "foo bar baz";
+
+    let t = thread::spawn(move || {
+        let mut s = assert_ok!(TcpStream::connect(&addr));
+
+        let t2 = thread::spawn(move || {
+            let mut s = assert_ok!(TcpStream::connect(&addr));
+            let mut b = vec![0; msg.len() * N];
+            assert_ok!(s.read_exact(&mut b));
+            b
+        });
+
+        let mut expected = Vec::<u8>::new();
+        for _i in 0..N {
+            expected.extend(msg.as_bytes());
+            let res = assert_ok!(s.write(msg.as_bytes()));
+            assert_eq!(res, msg.len());
+        }
+
+        (expected, t2)
+    });
+
+    let (mut a, _) = assert_ok!(srv.accept().await);
+    let (mut b, _) = assert_ok!(srv.accept().await);
+
+    let n = assert_ok!(tokio::io::copy(&mut a, &mut b).await);
+
+    let (expected, t2) = t.join().unwrap();
+    let actual = t2.join().unwrap();
+
+    assert!(expected == actual);
+    assert_eq!(n, msg.len() as u64 * 1024);
+}