tests: drivers: watchdog: Add negative test cases for Watchdog

Extend test coverage by adding tests that check invalid use
of the Watchdog API.

Signed-off-by: Sebastian Głąb <[email protected]>

Author: nordic-segl

tests/drivers/watchdog/wdt_error_cases/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(wdt_error_cases)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

tests/drivers/watchdog/wdt_error_cases/README.txt

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+This test suite contains negative test cases for the Watchdog driver.
+Test scenarios validate that invalid use of the watchdog driver
+returns error code as described in the API documentation
+(or Assertion Fail as explained below).
+
+Ideally, the driver shall be fully compliant with the documentation.
+However, it may happen that invalid function call results in
+Assertion Fail instead of error code.
+Since, main goal is to detect (and report) invalid use of the driver,
+both error code and assertion fail set test result as passed.
+See for example test_02_wdt_setup_before_setting_timeouts where
+ztest_set_assert_valid(true);
+is used to catch assertion fail.
+
+These tests were written to increase test coverage for the Watchdog driver.
+Since, coverage data is stored in the RAM, it is lost when watchdog fires.
+Therefore, in all test cases watchdog shall NOT expire.
+Use other sample to verify positive scenario for the watchdog driver.
+
+These tests were prepared on a target that had a bug in the wdt_disable()
+implementation. As a temporary remedy, order of tests was imposed.
+Since, tests are executed alphabetically, order was set by starting
+each test name with f.e. 'test_08b_...'.
+
+
+Tests are based on the watchdog API documentation available here:
+https://docs.zephyrproject.org/latest/hardware/peripherals/watchdog.html
+
+
+Follow these guidelines when enabling test execution on a new target.
+
+1. Although, code defines WDT_DISABLE_SUPPORTED but it was tested on a
+   target that supports disabling the watchdog.
+   Multiple tests call wdt_setup() which starts the watchdog.
+   Every test assumes that watchdog is disabled at startup.
+   As a result, executing this test suite on a target that doesn't
+   support wdt_disable() may require changes to the code.
+   When target supports wdt_disable() then extend WDT_TEST_FLAGS with:
+   #define WDT_TEST_FLAGS (... | WDT_DISABLE_SUPPORTED)
+
+2. There are three watchdog flags that can be passed to wdt_install_timeout():
+    - WDT_FLAG_RESET_NONE - when watchdog expires, it's callback is serviced but
+      reset doesn't occur.
+    - WDT_FLAG_RESET_CPU_CORE - when watchdog expires, only one core is reset, while
+      other cores are not affected.
+    - WDT_FLAG_RESET_SOC - when watchdog expires, target as "a whole" is reset.
+   Support for these flags varies between vendors and products.
+   a) List all supported flags in
+      #define WDT_TEST_FLAGS (... | WDT_FLAG_RESET_NONE_SUPPORTED |
+                              WDT_FLAG_RESET_CPU_CORE_SUPPORTED |
+                              WDT_FLAG_RESET_SOC_SUPPORTED)
+   b) Set supported flag in
+      #define DEFAULT_FLAGS (WDT_FLAG_RESET_SOC)
+      This define will be used in wdt_install_timeout() "correct" test step.
+
+3. These tests assume that watchdog driver supports multiple timeouts. Set
+   #define MAX_INSTALLABLE_TIMEOUTS (8)
+
+4. When all watchdog timeouts must have exactly the same watchdog timeout value
+   then extend WDT_TEST_FLAGS with:
+   #define WDT_TEST_FLAGS (... | WDT_FLAG_ONLY_ONE_TIMEOUT_VALUE_SUPPORTED)
+
+5. Set maximal allowed watchdog timeout value, f.e.:
+   #define WDT_WINDOW_MAX_ALLOWED (0xFFFFFFFFU)
+   Also, test assumes that minimal allowed watchdog timeout value must be zero.
+
+6. There are two watchdog options that can be passed to wdt_setup():
+    - WDT_OPT_PAUSE_IN_SLEEP;
+    - WDT_OPT_PAUSE_HALTED_BY_DBG.
+   Support for these options varies between vendors and products.
+   a) List all supported options in
+      #define WDT_TEST_FLAGS (... | WDT_OPT_PAUSE_IN_SLEEP_SUPPORTED |
+                              WDT_OPT_PAUSE_HALTED_BY_DBG_SUPPORTED)
+   b) Set supported option(s) in
+      #define DEFAULT_OPTIONS (WDT_OPT_PAUSE_IN_SLEEP | WDT_OPT_PAUSE_HALTED_BY_DBG)
+      This define will be used in wdt_setup() "correct" test step.
+
+7. When wdt_feed() can stall, extend WDT_TEST_FLAGS with:
+   #define WDT_TEST_FLAGS (... | WDT_FEED_CAN_STALL)

tests/drivers/watchdog/wdt_error_cases/boards/nrf54l15pdk_nrf54l15_cpuapp.overlay

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+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&wdt31 {
+	status = "okay";
+};

tests/drivers/watchdog/wdt_error_cases/prj.conf

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+CONFIG_ZTEST=y
+CONFIG_ZTEST_ASSERT_HOOK=y
+CONFIG_WATCHDOG=y