Testing with Unity and CMock

The nRF Connect SDK provides support for writing unit tests using Unity and CMock. Unity is a C unit test framework. CMock is a framework for generating mocks based on a header API. Support for CMock is integrated into Unity.

CMake automatically generates the required test runner file and the mock files. The test can be executed on the Native POSIX execution (native_posix) board.

Setting up a unit test

An example for a unit test can be found in tests/unity/example_test. The file tests/unity/example_test/CMakeLists.txt shows how to set up the generation of the test runner file and mocks.

To run the unit test, enable the Unity module (CONFIG_UNITY) and the module under test. The module under test and all dependencies are enabled and compiled into the binary, even the mocked modules.

The linker replaces all calls to the mocked API with a mock implementation using the wrapping feature. For example, -Wl,--wrap=foo replaces every call to foo() with a call to __cmock_foo(). Because of that, all mock functions are prefixed with __cmock (for example, __cmock_foo_Expect() instead of foo_Expect()).

To specify the APIs that should be mocked in a given test, edit CMakeLists.txt to call cmock_handle with the header file and, optionally, the relative path to the header as arguments. The relative path is needed if a file is included as, for example, #include <zephyr/bluetooth/gatt.h>. In this case, the relative path is bluetooth.

Add a line similar to the following in CMakeLists.txt to generate the mocks:

cmock_handle(${ZEPHYR_BASE}/include/bluetooth/gatt.h bluetooth)

The test runner file must be generated from the file that contains the tests. Unity treats all functions that are prefixed with test_ as tests.

Add a line similar to the following in CMakeLists.txt to generate the test runner file:


Running the test

Enter the following command to generate the test project (including the test runner file and the mocks) and run it:

west build -b native_posix -t run