test: add hal ticker test (us + lp tickers)

This test exercises ticker API
- init should be executed just once
- read timestamp

Set interrupt should be tested via upper layer, as it does not provide
API to change handler that is invoked in the ISR ticker handler.

TESTS/mbed_hal/lp_us_tickers/main.cpp

@@ -0,0 +1,110 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2017 ARM Limited
+ *
+ * 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.
+ */
+#include "utest/utest.h"
+#include "unity/unity.h"
+#include "greentea-client/test_env.h"
+
+#include "mbed.h"
+#include "us_ticker_api.h"
+#include "ticker_api.h"
+
+using namespace utest::v1;
+
+namespace {
+    volatile bool complete;
+    const ticker_interface_t* intf;
+}
+
+/* Ticker init should be run just once, thus read should always return a value that 
+ * increases (no reset).
+ */
+void test_ticker_init(void)
+{
+    intf->init();
+    uint32_t previous = intf->read();
+
+    intf->init();
+    uint32_t current = intf->read();
+    TEST_ASSERT_TRUE_MESSAGE(previous <= current, "init() changed the counter");
+
+    previous = intf->read();
+    intf->init();
+    current = intf->read();
+    TEST_ASSERT_TRUE_MESSAGE(previous <= current, "init() changed the counter");
+}
+
+/* Read multiple times, each returned time should be bigger than the previous one
+ * Counter up.
+ */
+void test_ticker_read(void)
+{
+    // this test assumes that to wrap around we would need to run >60 minutes
+    // therefore wrapping should not happen - previous <= current
+    const uint32_t test_loop = 15000;
+    uint32_t previous = intf->read();
+    uint32_t current;
+    for (uint32_t i = 0UL; i < test_loop; i++) {
+        current = intf->read();
+        TEST_ASSERT_TRUE_MESSAGE(previous <= current, "us ticker counter wrapped around");
+    }
+}
+
+/* Implement simple read while loop to check if time is increasing (counter up)
+ */
+void test_ticker_read_loop()
+{
+    uint32_t future_time = intf->read() + 10000UL;
+    while (intf->read() < future_time);
+    TEST_ASSERT_TRUE_MESSAGE(future_time <= intf->read(), "Future time is in the past");
+}
+
+utest::v1::status_t us_ticker_setup(const Case *const source, const size_t index_of_case)
+{
+    intf = get_us_ticker_data()->interface;
+    return greentea_case_setup_handler(source, index_of_case);
+}
+
+#if DEVICE_LOWPOWERTIMER
+utest::v1::status_t lp_ticker_setup(const Case *const source, const size_t index_of_case)
+{
+    intf = get_lp_ticker_data()->interface;
+    return greentea_case_setup_handler(source, index_of_case);
+}
+#endif
+
+Case cases[] = {
+    Case("us ticker HAL - Init", us_ticker_setup, test_ticker_init),
+    Case("us ticker HAL - Read", us_ticker_setup, test_ticker_read),
+    Case("us ticker HAL - Read in the loop", us_ticker_setup, test_ticker_read_loop),
+#if DEVICE_LOWPOWERTIMER
+    Case("lp ticker HAL - Init", lp_ticker_setup, test_ticker_init),
+    Case("lp ticker HAL - Read", lp_ticker_setup, test_ticker_read),
+    Case("lp ticker HAL - Read in the loop", lp_ticker_setup, test_ticker_read_loop),
+#endif
+};
+
+utest::v1::status_t greentea_test_setup(const size_t number_of_cases) 
+{
+    GREENTEA_SETUP(20, "default_auto");
+    return greentea_test_setup_handler(number_of_cases);
+}
+
+Specification specification(greentea_test_setup, cases, greentea_test_teardown_handler);
+
+int main() 
+{
+    Harness::run(specification);
+}