Writing tests

How to:

While C doesn’t have a built-in testing framework like some other languages, you can still write effective tests using assert.h for simple assertions or integrate third-party frameworks like CUnit or Unity for more structured testing. Here’s a basic example using assert.h to test a function that adds two integers:

#include <assert.h>
#include "my_math.h"

void test_addition() {
    assert(add(1, 2) == 3);
    assert(add(-1, -2) == -3);
    assert(add(0, 0) == 0);
    printf("All addition tests passed.\n");

int main() {
    return 0;

In my_math.h, you might have:

// Simple addition function
int add(int a, int b) {
    return a + b;

Running the test function in your main function outputs:

All addition tests passed.

For a more comprehensive testing setup using a framework like Unity, you would incorporate the framework into your project, then write test cases similarly, but utilizing the framework’s API for assertions and test running.

Deep Dive

Testing in C has historically been a manual and somewhat ad hoc process due to the language’s low-level nature and the lack of a standardized testing framework. This manual approach often led to less thorough testing practices compared to languages with built-in testing support. As the C language has been crucial in the development of foundational software systems, this lack of formal testing frameworks prompted the C community to develop third-party solutions, like CUnit and Unity.

These tools, while external to the standard C library, provide functionality akin to testing frameworks in other languages, offering a structured way to define, run, and evaluate tests. They help bridge the gap between C’s powerful system-level access and the modern development practice of automated testing. It’s worth noting that while these tools greatly enhance the testing process in C, they can introduce a learning curve and increase the complexity of project setup compared to languages with integrated testing support. Thus, for projects where reliability and maintainability are paramount, the investment in setting up a proper testing environment in C is well justified, even in light of possible alternatives.