add tests for io::timeout

tests/io_timeout.rs

@@ -0,0 +1,40 @@
+use std::time::Duration;
+
+use async_std::io;
+use async_std::task;
+
+#[test]
+#[should_panic(expected = "timed out")]
+fn io_timeout_timedout() {
+    task::block_on(async {
+        io::timeout(Duration::from_secs(1), async {
+            let stdin = io::stdin();
+            let mut line = String::new();
+            let _n = stdin.read_line(&mut line).await?;
+            Ok(())
+        })
+        .await
+        .unwrap(); // We should panic with a timeout error
+    });
+}
+
+#[test]
+#[should_panic(expected = "My custom error")]
+fn io_timeout_future_err() {
+    task::block_on(async {
+        io::timeout(Duration::from_secs(1), async {
+            Err::<(), io::Error>(io::Error::new(io::ErrorKind::Other, "My custom error"))
+        })
+        .await
+        .unwrap(); // We should panic with our own error
+    });
+}
+
+#[test]
+fn io_timeout_future_ok() {
+    task::block_on(async {
+        io::timeout(Duration::from_secs(1), async { Ok(()) })
+            .await
+            .unwrap(); // We shouldn't panic at all
+    });
+}