Add simulated Read/Write fragmentation test

tests/common/mod.rs

@@ -4,7 +4,7 @@ use async_std::path::PathBuf;
 use async_std::sync::Arc;
 use async_std::task::{Context, Poll};
 use std::pin::Pin;
-use std::sync::Mutex;
+use std::sync::{atomic::AtomicBool, Mutex};
 
 #[derive(Debug, Copy, Clone)]
 #[allow(dead_code)]
@@ -19,6 +19,12 @@ pub struct TestCase {
     source_fixture: Arc<File>,
     expected_fixture: Arc<Mutex<File>>,
     result: Arc<Mutex<File>>,
+    throttle: Arc<Throttle>,
+}
+
+enum Throttle {
+    NoThrottle,
+    YieldPending(AtomicBool, AtomicBool),
 }
 
 impl TestCase {
@@ -68,9 +74,18 @@ impl TestCase {
             source_fixture: Arc::new(source_fixture),
             expected_fixture: Arc::new(Mutex::new(expected_fixture)),
             result,
+            throttle: Arc::new(Throttle::NoThrottle),
         }
     }
 
+    #[allow(dead_code)]
+    pub fn throttle(&mut self) {
+        self.throttle = Arc::new(Throttle::YieldPending(
+            AtomicBool::new(false),
+            AtomicBool::new(false),
+        ));
+    }
+
     pub async fn read_result(&self) -> String {
         use async_std::prelude::*;
         let mut result = String::new();
@@ -128,13 +143,42 @@ impl Read for TestCase {
         cx: &mut Context,
         buf: &mut [u8],
     ) -> Poll<io::Result<usize>> {
-        Pin::new(&mut &*self.source_fixture).poll_read(cx, buf)
+        match &*self.throttle {
+            Throttle::NoThrottle => Pin::new(&mut &*self.source_fixture).poll_read(cx, buf),
+            Throttle::YieldPending(read_flag, _) => {
+                if read_flag.fetch_xor(true, std::sync::atomic::Ordering::SeqCst) {
+                    cx.waker().wake_by_ref();
+                    Poll::Pending
+                } else {
+                    // read partial
+                    let throttle_len = std::cmp::min(buf.len(), 10);
+                    let buf = &mut buf[..throttle_len];
+                    let ret = Pin::new(&mut &*self.source_fixture).poll_read(cx, buf);
+                    ret
+                }
+            }
+        }
     }
 }
 
 impl Write for TestCase {
     fn poll_write(self: Pin<&mut Self>, cx: &mut Context, buf: &[u8]) -> Poll<io::Result<usize>> {
-        Pin::new(&mut &*self.result.lock().unwrap()).poll_write(cx, buf)
+        match &*self.throttle {
+            Throttle::NoThrottle => {
+                Pin::new(&mut &*self.result.lock().unwrap()).poll_write(cx, buf)
+            }
+            Throttle::YieldPending(_, write_flag) => {
+                if write_flag.fetch_xor(true, std::sync::atomic::Ordering::SeqCst) {
+                    cx.waker().wake_by_ref();
+                    Poll::Pending
+                } else {
+                    // write partial
+                    let throttle_len = std::cmp::min(buf.len(), 10);
+                    let buf = &buf[..throttle_len];
+                    Pin::new(&mut &*self.result.lock().unwrap()).poll_write(cx, buf)
+                }
+            }
+        }
     }
 
     fn poll_flush(self: Pin<&mut Self>, cx: &mut Context) -> Poll<io::Result<()>> {

tests/fixtures/response-chunked-echo-throttled.txt

@@ -0,0 +1,17 @@
+HTTP/1.1 200 OK
+transfer-encoding: chunked
+date: {DATE}
+content-type: text/plain
+
+1
+M
+6
+ozilla
+9
+Developer
+5
+Netwo
+2
+rk
+0
+

tests/server.rs

@@ -77,6 +77,33 @@ async fn test_chunked_echo() {
     case.assert().await;
 }
 
+#[async_std::test]
+async fn test_chunked_echo_throttled() {
+    let mut case = TestCase::new_server(
+        "fixtures/request-chunked-echo.txt",
+        "fixtures/response-chunked-echo-throttled.txt",
+    )
+    .await;
+    case.throttle();
+    let addr = "http://example.com";
+
+    async_h1::accept(addr, case.clone(), |req| async {
+        let mut resp = Response::new(StatusCode::Ok);
+        let ct = req.content_type();
+        let body: Body = req.into();
+        resp.set_body(body);
+        if let Some(ct) = ct {
+            resp.set_content_type(ct);
+        }
+
+        Ok(resp)
+    })
+    .await
+    .unwrap();
+
+    case.assert().await;
+}
+
 #[async_std::test]
 async fn test_unexpected_eof() {
     // We can't predict unexpected EOF, so the response content-length is still 11