How teams keep firmware right as it grows: readable code, modules behind narrow interfaces, fakes, tests on boot, test-first fixes, safe refactors and code review. Ends with a messy sketch refactored under test.
0 of 7 done
7 lessons in 4 chapters, about 7 hours on a simulated Arduino Uno R3. Free, in your browser, every step checked by the simulator.
A thermostat that only knows a TempSensor interface: a real TMP36 and a fake behind the same door, a rehearsal with the fake on boot, a move into sensor.h, and a calibration added without touching the thermostat.
Open it in the simulatorA bug report against a countdown that passes all its tests: reproduce it on the hardware, pin it to one pure function, write the test that fails, fix it, triangulate the edges, and close the report.
Open it in the simulatorCommits, branches, diffs and pull requests explained properly, then a real review: a teammate's pull request with a millis() rollover, an off-by-one and an int overflow, each caught by a checklist question and proven fixed by the self-test.
Open it in the simulatorEach lesson opens when the one before it is done, and each chapter ends in a project.
Names, one job per function, and modules behind a narrow interface.
A thermostat sketch that works and lies: one-letter names, magic numbers that drifted apart, one loop doing four jobs. Name the numbers, give each job a function, and read loop() like a table of contents.
0 of 7 steps
A thermostat that only knows a TempSensor interface: a real TMP36 and a fake behind the same door, a rehearsal with the fake on boot, a move into sensor.h, and a calibration added without touching the thermostat.
0 of 6 steps
A harness in twenty lines, then bugs fixed test first.
A test harness in twenty lines: a CHECK macro that prints PASS or FAIL with the line and the condition, a summary line and a red or green lamp. Test the edges, meet a real failure, fix it, and switch the tests off for a release.
0 of 7 steps
A bug report against a countdown that passes all its tests: reproduce it on the hardware, pin it to one pure function, write the test that fails, fix it, triangulate the edges, and close the report.
0 of 7 steps
Refactors under test, and the review and git habits of a team.
A Beaufort wind scale as an if chain and a switch, reshaped into two tables with its tests green after every step: replace a conditional with a table, prove the net catches a slip, extract a function, and add a feature in one line.
0 of 7 steps
Commits, branches, diffs and pull requests explained properly, then a real review: a teammate's pull request with a millis() rollover, an off-by-one and an int overflow, each caught by a checklist question and proven fixed by the self-test.
0 of 6 steps
A messy dice sketch, fixed test first and refactored under its own self-test.
The gallery's electronic dice after a game night of quick fixes: one-letter names, an if chain, pasted code and a bug report. Fix the bug test first, then refactor it clean, one step at a time, with the self-test saying all pass after every run.
0 of 8 steps
All 7 lessons, in order, each with what it covers. Any of them opens in the editor right away.
Software design and testing is part of the coding track, a ladder of courses from zero to expert.
Python and C++ from your first print to classes, tests and state machines. Every program runs on a simulated board, so a bug is something you can see.
See every course on the trackEvery lesson runs in the simulator with nothing to buy. When you want the real thing, these kits have the parts.
Pick the starter kit you own and run every lesson in its manual with the same parts on the same pins.
See every kitYes. All 7 lessons of Software design and testing are free and run in your browser, with nothing to install and no parts to buy before you start.
No. Every lesson runs on a simulated Arduino Uno R3 with its parts on the canvas, and the simulator checks each step as you go. When you want to build it for real, the same wiring and code work on a real board.
About 7 hours: 7 lessons in 4 chapters, each one a few short steps. Your progress is kept, so you can stop after any lesson and pick up where you left off.
Each chapter ends in a project that puts it together: Modules and interfaces, Test-driven fixes and Code review and git, explained.
With "Clean functions and naming", and each lesson builds on the one before it. New to circuits? Electronics basics is the course that starts from zero.