Add timestamp pallet test (#340)

* Add timestamp pallet test

* Remove println

* Make timestamp test more reliable

tests/integration/frame/mod.rs

@@ -21,3 +21,4 @@ mod contracts;
 mod staking;
 mod sudo;
 mod system;
+mod timestamp;

tests/integration/frame/timestamp.rs

@@ -0,0 +1,48 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of subxt.
+//
+// subxt is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// subxt is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with subxt.  If not, see <http://www.gnu.org/licenses/>.
+
+use crate::test_context;
+use std::time::{
+    SystemTime,
+    UNIX_EPOCH,
+};
+
+#[async_std::test]
+async fn storage_get_current_timestamp() {
+    let sys_timestamp = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap()
+        .as_millis() as u64;
+    let cxt = test_context().await;
+
+    // wait until blocks are produced to get the timestamp
+    let mut sub = cxt.client().rpc().subscribe_blocks().await.unwrap();
+    let block_hash = loop {
+        if let Ok(Some(block)) = sub.next().await {
+            break block.hash()
+        }
+    };
+
+    let timestamp = cxt
+        .api
+        .storage()
+        .timestamp()
+        .now(Some(block_hash))
+        .await
+        .unwrap();
+
+    assert!(timestamp > sys_timestamp)
+}