Fix expect_read documentation

It was copied checked_write but never updated.

tests/util/mod.rs

@@ -211,11 +211,11 @@ macro_rules! checked_write {
     }};
 }
 
-/// A checked {write, send, send_to} macro that ensures the entire buffer is
-/// written.
+/// A checked {read, recv, recv_from, peek, peek_from} macro that ensures the
+/// current buffer is read.
 ///
-/// Usage: `expect_read!(stream.read(&mut buf), DATA);` writes into `buf`,
-/// comparing to `DATA`.
+/// Usage: `expect_read!(stream.read(&mut buf), DATA);` reads into `buf` and
+/// compares it to `DATA`.
 /// Also works for recv(_from): `expect_read!(socket.recv_from(&mut buf), DATA, address)`.
 macro_rules! expect_read {
     ($socket: ident . $method: ident ( $buf: expr $(, $arg: expr)* ), $expected: expr) => {{