Tooling and testing for Particle firmware
February 9th, 2020in warm-and-fuzzy
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Particle tooling

After originally building and deploying the Particle firmware code from my desktop, I wanted to get proper CI/CD put in place for it.
The Particle CLI let me do most of what I wanted but not quite all, so I stood up a small collection of helper scripts in JavaScript based on the oclif command-line framework.
Creating a custom build script wrapped around the particle-api-js library let me do nice things like excluding test code from firmware compilation.
Creating a custom upload script wrapped around curl (yeah yeah) let me solve one part of Particle’s aggravating approach to versioning: firmware has a uint16_t PRODUCT_VERSION that must be defined at build time and then provided at upload time, even though it’s also encoded in the binary. My script scans the source file for the definition of PRODUCT_VERSION and uses that to formulate the right API call. It’d still be nicer if this could all be more free-form (e.g. allow for git commit SHAs as a version ID) but this makes it at least somewhat less painful.
Side note: You’ll still see various one-off “whoops, I forgot to increment the PRODUCT_VERSION” commits in the codebase. Eesh.

Particle testing

I don’t write a lot of test code, but when I do, I have to mock stuff out. The firmware tests are primarily to test the setpoint scheduler as well as minor primitives like the queue type underlying all reporting back to the cloud.
Since this is C++, I chose catch2 as the test harness and it’s been lovely.
I stood up a whole bunch of mocks for all the stuff provided by the Particle environment that either I needed to control (like time) or just needed to be able to compile. It’s a little surprising that there isn’t already a ready-to-go version of this sort of stuff provided by Particle themselves.
Since I’d previously made gcc available from the Flatbuffers exercise, it was easy to compile and run this code as part of CI/CD using yet another custom test script — easier than doing it in package.json.
I don’t think I actually caught any bugs in the firmware code with these tests but I do feel a lot better knowing this complex bit of logic does have decent test coverage since — unlike with just about all the other code which really just transports data from here to there — the scheduler logic would fail in more subtle ways, particularly in ways that may lead to angry housemates.
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