ATmega TDD Example

This project demonstrates the use of unit testing and test-driven development (TDD) when writing bare-metal code for an ATmega series microcontroller. This project uses the ThrowTheSwitch/Unity unit testing framework together with meekrosoft/fff for mocking support in order to minimize the reliance on external dependencies such as Ruby.

In this example, the unit tests are run exclusively on the developer's machine (the "host") instead of on the microcontroller itself (the "target"). To streamline this process among developers, the project uses a Docker environment described below (see running unit tests).

Required Hardware

1. Breadboard
2. Microcontroller (ATmega168A, 28-PDIP Package)
3. LED
4. Current-limiting resistor
5. Programmer (e.g. Pololu USB AVR Programmer v2.1)
6. Some jumper wires

Details on how to connect these components can be found in Docs/schematic.pdf.

Running unit tests

This project uses a Dockerized environment from within which the unit tests can be executed. This saves developers from having to set up the development environment themselves on their local workstations.

First, make sure that you have Docker installed and running on your machine. Next, install and activate the Dev Containers extension for Visual Studio Code.

Opening the workspace in Visual Studio Code should then prompt you with a textbox that allows you to reopen the project in a Docker container with all required packages already installed. To invoke all unit tests, simply run:

./unit-tests.sh

This should show that all tests passing:

Further reading

• Grenning, J. W. (2011): Test-Driven Development for Embedded C. Raleigh, NC: Pragmatic Programmers.