How to abstract HAL in embedded test driven development?

Question

Recently I've been reading into topic of test driven development and decided to give it a go with a sensor driver I need. Sensor uses SPI interface and I will implement this driver on STM32F415 processor with help of CubeMX for project generation. After generating project, I have access to HAL SPI functions such as this:

HAL_StatusTypeDef HAL_SPI_Transmit(SPI_HandleTypeDef *hspi, uint8_t *pData, uint16_t Size, uint32_t Timeout)

I would create a header file called 'sensor_hall.h', put this SPI function declaration in it and then generate a mock of this header using CMock.

My questions are, is this a valid approach? Should I introduce more abstraction to this? And how to deal with the first argument, pointer to SPI struct when mocking?

Answer 1

Your instincts are correct and you are proposing a valid approach. There is no need to add more abstraction into the mix here.

Assuming there is also a HAL_SPI_* function to obtain (a pointer to) a spi struct, you can use a mock-specific version of a spi struct that contains useful members for your mocks.

If the spi struct needs to be declared directly by the client code (your sensor driver), then I would just verify in the mocks that consistently the same pointer is passed in.