[Tests] [pallet-timestamp] Add tests for OnTimestampSet. (#11323)

* NF: move tests mod to another file

* NF: separate test setup to mock mod

* test: check if OnTimestampSet ran correctly.

* docs: add license header.

* fixup! NF: separate test setup to mock mod

* NF: formatting changes

substrate/frame/timestamp/src/tests.rs

@@ -0,0 +1,52 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2020-2022 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Tests for the Timestamp module.
+
+use crate::mock::*;
+use frame_support::assert_ok;
+
+#[test]
+fn timestamp_works() {
+	new_test_ext().execute_with(|| {
+		Timestamp::set_timestamp(42);
+		assert_ok!(Timestamp::set(Origin::none(), 69));
+		assert_eq!(Timestamp::now(), 69);
+		assert_eq!(Some(69), get_captured_moment());
+	});
+}
+
+#[test]
+#[should_panic(expected = "Timestamp must be updated only once in the block")]
+fn double_timestamp_should_fail() {
+	new_test_ext().execute_with(|| {
+		Timestamp::set_timestamp(42);
+		assert_ok!(Timestamp::set(Origin::none(), 69));
+		let _ = Timestamp::set(Origin::none(), 70);
+	});
+}
+
+#[test]
+#[should_panic(
+	expected = "Timestamp must increment by at least <MinimumPeriod> between sequential blocks"
+)]
+fn block_period_minimum_enforced() {
+	new_test_ext().execute_with(|| {
+		Timestamp::set_timestamp(42);
+		let _ = Timestamp::set(Origin::none(), 46);
+	});
+}