Add a test for reading client preface

tests/server_preface.rs

@@ -0,0 +1,31 @@
+extern crate h2;
+extern crate http;
+extern crate futures;
+extern crate mock_io;
+extern crate env_logger;
+
+use h2::server;
+
+use futures::*;
+
+const SETTINGS: &'static [u8] = &[0, 0, 0, 4, 0, 0, 0, 0, 0];
+const SETTINGS_ACK: &'static [u8] = &[0, 0, 0, 4, 1, 0, 0, 0, 0];
+
+#[test]
+fn read_preface_in_multiple_frames() {
+    let _ = ::env_logger::init().unwrap();
+
+    let mock = mock_io::Builder::new()
+        .read(b"PRI * HTTP/2.0")
+        .read(b"\r\n\r\nSM\r\n\r\n")
+        .write(SETTINGS)
+        .read(SETTINGS)
+        .write(SETTINGS_ACK)
+        .read(SETTINGS_ACK)
+        .build();
+
+    let h2 = server::handshake(mock)
+        .wait().unwrap();
+
+    assert!(Stream::wait(h2).next().is_none());
+}