fix clippy::cognitive_complexity

tests/buf_writer.rs

@@ -4,6 +4,7 @@ use async_std::task;
 
 #[test]
 fn test_buffered_writer() {
+    #![allow(clippy::cognitive_complexity)]
     task::block_on(async {
         let inner = Vec::new();
         let mut writer = BufWriter::with_capacity(2, inner);

tests/channel.rs

@@ -37,6 +37,7 @@ fn capacity() {
 
 #[test]
 fn len_empty_full() {
+    #![allow(clippy::cognitive_complexity)]
     task::block_on(async {
         let (s, r) = channel(2);