How to Unit Test Arduino Code: A Comprehensive Guide

Testing Arduino code can be challenging due to the nature of embedded systems, but it's definitely possible. This article provides a step-by-step guide to help you set up unit tests for your Arduino projects.

Choosing a Testing Framework

One of the most popular frameworks for unit testing Arduino code is ArduinoUnit. Another option is AUnit, which is a more modern and feature-rich library. You can install these libraries through the Arduino Library Manager.

Setting Up Your Environment

1. Install the chosen testing library, such as ArduinoUnit or AUnit.

2. Create a new Arduino sketch or set of sketches for your tests. This helps you keep your tests separate from your main application code.

Writing Test Cases

Here's a basic structure of how to write a unit test using AUnit:

include AUnit.h
// Example function to test
int add(int a, int b) {
    return a   b
}
// Define test suite
void testAdd() {
    assertEqual(add(2, 3), 5)
    assertEqual(add(-1, 1), 0)
    assertEqual(add(0, 0), 0)
}
// Run all tests
void setup() {
    (9600)
    TestRunner::run()
}
void loop() {
    // No loop code for tests
}

Running Your Tests

Upload the test sketch to your Arduino board. Open the Serial Monitor to view the test results. The framework will output the results of each test indicating whether they passed or failed.

Mocking and Dependency Injection

For more complex code, you might need to mock certain parts of your code, like hardware interactions. This can be done by creating interfaces for your hardware interactions and using dependency injection to pass mock objects to your classes.

Continuous Integration (Optional)

If you're working on a larger project, consider setting up a continuous integration (CI) system to automatically run your tests whenever you push changes to your code repository. This can be done using platforms like GitHub Actions or Travis CI.

Platform-Specific Limitations

Keep in mind that unit tests run on your computer might not fully replicate the behavior of your code on the Arduino hardware. Testing libraries often provide ways to simulate hardware behavior, but it's essential to validate critical functionality on the actual hardware.

Example of Mocking

If you're using a library that interacts with hardware, you can create a mock class for testing:

class MockSensor {
public:
    int read() {
        return 42 // Mocked value
    }
}
void sensorTest() {
    MockSensor sensor
    assertEqual((), 42)
}

Conclusion

Unit testing Arduino code involves setting up a suitable testing framework, writing test cases, and optionally mocking dependencies. This process helps ensure that your code is functioning correctly and can make it easier to maintain and refactor your projects in the future.