Unit Testing in C

Coming from Javascript and Ruby development, I found it quite difficult to get unit tests running in C. This is a short tutorial on how to set up testing.

Installing Boost Test

Boost is a massive collection of C++ libraries. I haven’t had the time to look over the collection, but Boost Test Library provides the simple unit testing support I needed.

Creating a Test Module

#define BOOST_TEST_MODULE MyTestModule
#include <boost/test/included/unit_test.h>


That’s a barebones test module that will compile and run.

  • MyTestModule is the name of our module
  • BOOST_AUTO_TEST_CASE declares a test case
  • myTestCase is the name of the test case.
  • BOOST_CHECK accepts one parameter and asserts it is true

Simple Example

Take the following C++ header file useful.h.

#ifndef TEST_H
#define TEST_H

int usefulFunction (int val) {
  return val;


The function above simply returns any integer you give it. We can test it with the following file useful.spec.c:

#define BOOST_TEST_MODULE UsefulModule
#include <boost/test/included/unit_test.h>
#include "useful.h"

BOOST_AUTO_TEST_CASE(usefulFunctionTest) {
  BOOST_CHECK(usefulFunction(2) == 2);
  BOOST_CHECK(usefulFunction(3) == 3);

To run the tests:

  1. Compile using g++ -o useful.spec.o useful.spec.c
  2. Run with ./useful.spec.o