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Re: Unit testing for embedded development

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You need to understand the concept of "mocking" w.r.t.
interfaces and time. Then you need to structure your
implementation so that the real interfaces can be replaced
with the mock interfaces during testing.

By symmetry, to unit test the interfaces you need to have
many mock applications.


On 18/05/18 08:18, pozz wrote:
> I'm not an expert on test-driven development. I know the general ideas behind 
> TDD, however I never used it in my projects.
> 
> I want to start using TDD, at least creating some unit testing on some more 
> critical units. However I have many difficulties.
> 
> For a module that calculates a checksum, it is very simple to create a unit 
> test. However an embedded firmware is more complex.
> 
> Consider a simple example. When the user press button 1, a buzzer must be 
> activated for 1 second.
> 
> ----- Start of buzzer.c -----
> #include "timer.h"
> #include "bsp.h"
> 
> statis Timer tmr_buzzer;
> 
> void buzzer_on(uint16 time_ms) {
>    TimerSet(&tmr_buzzer, time_ms);
>    bsp_buzzer_on();
> }
> 
> void buzzer_off(void) {
>    bsp_buzzer_off();
> }
> 
> void buzzer_task(void) {
>    if (TimerExpired(&tmr_buzzer)) {
>      buzzer_off();
>    }
> }
> ----- End of buzzer.c -----
> 
> Of course I have a bsp.c/bsp.h and a timer.c/timer.h.
> 
> Now I want to create a unit test for buzzer module, to run on PC.
> 
> ----- Start of test_buzzer.c -----
> #include <stdbool.h>
> #include "timer.h"   /* driver for PC testing */
> #include "bsp.h"     /* bsp_buzzer_on/off declarations */
> 
> static bool buzzer_on;
> 
> int main(int argc, char *argv[]) {
>    /* Test if buzzer_on() works */
>    buzzer_on(10000);
>    if (!buzzer_on) ... test failed ...
>    /* Wait for 10010 ms */
>    if (buzzer_on)  ... test failed ...
> 
>    ...
> }
> 
> void bsp_buzzer_on(void)  { buzzer_on = true; }
> void bsp_buzzer_off(void) { buzzer_on = false; }
> 
> ----- End of test_buzzer.c -----
> 
> 
> How do you simulate passing of the time (wait for 1010ms)? Of course, I don't 
> want to wait 10 seconds for the test.  I need to speed up the time.
> 
> Is this the correct way to create a unit testing for a buzzer library?

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Unit testing for embedded development pozz <pozzugno@gmail.com> - 2018-05-18 09:18 +0200
  Re: Unit testing for embedded development Tobias Baumann <tobias.baumann@elpra.de> - 2018-05-18 10:10 +0200
  Re: Unit testing for embedded development Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-05-18 09:17 +0100
  Re: Unit testing for embedded development Paul Rubin <no.email@nospam.invalid> - 2018-05-18 01:23 -0700
  Re: Unit testing for embedded development StateMachineCOM <statemachineguru@gmail.com> - 2018-05-19 08:15 -0700

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