Simple Unit Testing for Types in C11

Sometimes I find myself doing coding tests to keep my problem-solving skills sharp. One of the platforms I use is CodeWars, a platform owned by Andela. My current stack is JavaScript (including NodeJS), PHP, and C/C++. I noticed the tests for the C and C++ exercises were written using a library called Criterion, which brings us to the topic of Unit testing in C and C++.  I did some intense C and C++ work a while back on embedded Linux systems and one of the tools I lacked was a simple library to do testing in. Looking at the criterion I realized I had just found an easy-to-use tool for testing my C/C++ work.

I decided to put this simplicity to test and in order to do so I decided to use a toy CLI app I wrote in C some years ago. This app has a function for random number generation.

In file app.c:

#include<stdio.h>
#include<time.h>
#include<stdlib.h>
#include<string.h>
#include "app.h"
........
int generateAccountNumber(){
    srand(time(NULL));
    return rand();
}
........

Testing this is as simple as the code below:

In file tests.c:

#include <stdio.h>
#include <criterion/criterion.h>
#include "app.h"
#include <string.h>

#define DETERMINE_TYPE(x) _Generic((x), \
    int: "int", \
    float: "float", \
    double: "double", \
    char: "char", \
    long: "long", \
    default: "unknown")

Test(bankapp, random_num) {
    cr_assert(!strcmp("int", DETERMINE_TYPE(generateAccountNumber())));
}

All you need to do now is compile the test using:

gcc tests.c app.c -o tests -lcriterion

One thing to note is that the main function of the application you are testing must be in a separate file to prevent clashing with the main file provided by the Criterion testing framework. And that is it! You have a test.

I added the C11 _Generic macro feature to highlight a new C language feature that allows you to “return” a select value or function based on the type provided. This can be used for implementing programming features such as function overloading, Generics, Type checking like I used here, and many more. We will be looking more into this C11 feature in future articles. Thanks for reading.

References

1. Criterion Testing Framework Documentation.
2. Blog on how to use Generic Macros in C.