[toranj] add test to verify child sending data poll within its timeout (#4136)

This commit adds a `toranj` test-case. This test covers the situation
where the data poll interval is set to a value larger than child's
timeout interval. The test verifies that the sleepy child would send a
data poll within its timeout interval (ensuring that child stays in
parent's child table).

tests/toranj/start.sh

@@ -137,6 +137,7 @@ run test-031-meshcop-joiner-commissioner.py
 run test-032-child-attach-with-multiple-ip-addresses.py
 run test-033-mesh-local-prefix-change.py
 run test-034-poor-link-parent-child-attach.py
+run test-035-child-timeout-large-data-poll.py
 run test-100-mcu-power-state.py
 run test-600-channel-manager-properties.py
 run test-601-channel-manager-channel-change.py

tests/toranj/test-035-child-timeout-large-data-poll.py

@@ -0,0 +1,83 @@
+#!/usr/bin/env python
+#
+#  Copyright (c) 2019, The OpenThread Authors.
+#  All rights reserved.
+#
+#  Redistribution and use in source and binary forms, with or without
+#  modification, are permitted provided that the following conditions are met:
+#  1. Redistributions of source code must retain the above copyright
+#     notice, this list of conditions and the following disclaimer.
+#  2. Redistributions in binary form must reproduce the above copyright
+#     notice, this list of conditions and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#  3. Neither the name of the copyright holder nor the
+#     names of its contributors may be used to endorse or promote products
+#     derived from this software without specific prior written permission.
+#
+#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+#  POSSIBILITY OF SUCH DAMAGE.
+
+import wpan
+import time
+
+# -----------------------------------------------------------------------------------------------------------------------
+# Test description:
+#
+# This test covers the situation where the data poll interval is set to a value larger than child's timeout interval.
+# The test verifies that the sleepy child would send a data poll within its timeout interval (ensuring hat child stays
+# in parent's child table).
+
+test_name = __file__[:-3] if __file__.endswith('.py') else __file__
+print('-' * 120)
+print('Starting \'{}\''.format(test_name))
+
+# -----------------------------------------------------------------------------------------------------------------------
+# Creating `wpan.Nodes` instances
+
+speedup = 4
+wpan.Node.set_time_speedup_factor(speedup)
+
+parent = wpan.Node()
+child = wpan.Node()
+
+# -----------------------------------------------------------------------------------------------------------------------
+# Init all nodes
+
+wpan.Node.init_all_nodes()
+
+# -----------------------------------------------------------------------------------------------------------------------
+# Test implementation
+
+parent.form("poll-timeout")
+
+TIMEOUT = 5   # Child timeout in seconds
+
+child.set(wpan.WPAN_THREAD_CHILD_TIMEOUT, str(TIMEOUT))
+
+child.set(wpan.WPAN_POLL_INTERVAL, str(5 * TIMEOUT * 1000))
+
+child.join_node(parent, node_type=wpan.JOIN_TYPE_SLEEPY_END_DEVICE)
+
+poll_count_before = int(child.get(wpan.WPAN_NCP_COUNTER_TX_PKT_DATA_POLL), 0)
+
+time.sleep(TIMEOUT * 1.1 / speedup)
+
+poll_count_after = int(child.get(wpan.WPAN_NCP_COUNTER_TX_PKT_DATA_POLL), 0)
+
+wpan.verify(poll_count_after > poll_count_before)
+
+# -----------------------------------------------------------------------------------------------------------------------
+# Test finished
+
+wpan.Node.finalize_all_nodes()
+
+print('\'{}\' passed.'.format(test_name))