7.2.3. How to use Unit Tests

Verify that the unit testing framework is working as expected:

.\fox.ps1 waf build_app_unit_test_gcc

Typical usage and more information on the unit tests can be found in Unit tests.

7.2.3.1. Guidelines for the Unit Test Skeleton

Note

This example

In this example a driver that resides in src/app/driver/<driver>/<driver>.c and src/app/driver/<driver>/<driver>.h is added and therefore the accompanying unit tests need to be added also. The module abc.c implements the public function extern uint8_t ABC_DoThis(void) and the static function static uint8_t ABC_DoSomethingElse(uint8_t someArgument). Therefore, there are now two functions that need to be united tested.

At first the accompanying unit test file needs to be created in tests/unit/app/driver/abc/test_abc.c (notice the prefix test) based on the template in conf/tpl/test_c.c.

7.2.3.2. Public/Extern Function Tests

  1. Add a function uint8_t testABC_DoThis() in the appropriate section in the test file tests/unit/app/driver/abc/test_abc.c. This function implements the tests for ABC_DoThis(). The prefix test (no trailing underscore) is required for CMock to detect the function as a test-function.

  2. Write the test code.

7.2.3.3. Static Function Tests

  1. Static functions are not seen by other translation units, therefore the static functions must be made callable from other modules by creating a wrapper. For this example the wrapper will be extern uint8_t TEST_ABC_DoSomethingElse(uint8_t someArgument) (notice the TEST_ prefix followed by the name of the static function).

  2. The declaration of the wrapper needs to be placed in the appropriate section in the header of the driver (src/app/driver/<driver>/<driver>.h).

  3. The definition of the wrapper needs to be placed in the appropriate section in the source of the driver (src/app/driver/<driver>/<driver>.c). The only thing this wrapper needs to do, is to verbatim pass all arguments to the original function (i.e., the static function) and return its result. The definition of the wrapper looks therefore like this

    1extern uint8_t testABC_DoSomethingElse(uint8_t someArgument) {
2    return ABC_DoSomethingElse(someArgument);
3}

  4. Add a function void testABC_DoSomethingElse(void) in the appropriate section in the test file tests/unit/app/driver/abc/test_abc.c. This function implements the tests for ABC_DoSomethingElse(). The prefix test (no trailing underscore) is required for CMock to detect the function as a test-function. Note: The TEST_ prefix of the externalization wrapper is removed and not part of the test function name.

  5. Write test code.

7.2.3.4. Result

Listing 7.46 Header of the abc-driver (src/app/driver/<driver>/<driver>.h)
1/*========== Extern Function Prototypes =====================================*/
2extern uint8_t ABC_DoThis(void);
3
4/*========== Externalized Static Functions Prototypes (Unit Test) ===========*/
5#ifdef UNITY_UNIT_TEST
6extern uint8_t TEST_ABC_DoSomethingElse(uint8_t someArgument);
7#endif

The wrapper function TEST_ABC_DoSomethingElse needs to be put inside the UNITY_UNIT_TEST guard, so that it is not build during target builds.

Listing 7.47 Implementation of the abc-driver (src/app/driver/<driver>/<driver>.c)
 1/*========== Static Function Prototypes =====================================*/
 2static uint8_t ABC_DoSomethingElse(uint8_t someArgument);
 3
 4/*========== Static Function Implementations ================================*/
 5static uint8_t ABC_DoSomethingElse(uint8_t someArgument) {
 6    return someArgument;
 7}
 8
 9/*========== Extern Function Implementations ================================*/
10extern uint8_t ABC_DoThis(void) {
11    return ABC_DoSomethingElse(1);
12}
13
14/*========== Externalized Static Function Implementations (Unit Test) =======*/
15#ifdef UNITY_UNIT_TEST
16extern uint8_t TEST_ABC_DoSomethingElse(uint8_t someArgument) {
17    return ABC_DoSomethingElse(someArgument);
18}
19#endif
Listing 7.48 Implementation of the abc-driver test (tests/unit/app/driver/abc/test_abc.c)
1void testABC_DoThis(void) {
2    /* test code */
3    ABC_DoThis();
4}
5
6void testABC_DoSomethingElse() {
7    /* test code */
8    TEST_ABC_DoSomethingElse(2);
9}

7.2.4. Linux specific Usage

The unit test suite is developed on Windows and there works out of the box on all setup that install the dependencies as they are specified in Software Installation. However, it is still possible to get the unit test suite working on Linux. Internally it is tested with the following setup:

  • cat /etc/redhat-release: AlmaLinux release 10.2 (Lavender Lion)

  • uname -mrs: Linux 6.12.0-211.7.3.el10_2.x86_64 x86_64

  • gcc --version: gcc (GCC) 14.3.1 20251022 (Red Hat 14.3.1-4)

  • ruby --version: ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [x86_64-linux]

7.2.5. Unit Test Macros

  • UNITY_UNIT_TEST: shall be used to exclude code that is not needed for the target build, but required for unit testing (e.g., making a static function testable). It shall not be used to change functional behavior when compiling (some rare exceptions to this rule can be found in the code, but it is generally not preferred to do so, although sometimes it is needed.)

  • COMPILE_FOR_UNIT_TEST: shall be used when code needs to be compiled differently in oder to make it unit testable on the host. Do not use UNITY_UNIT_TEST to achieve the same (see above).