Unit test for a C program

Question

I've a C program that gives prime numbers up to the input number. I want to test this program, and see if it gives composite numbers. Now I need to implement the test, which I find difficult. So I'll appreciate if anybody can help me.

Here is my Checkprime.c:

#include "defs.h"
#include "externs.h"
#include "minunit.h"

int CheckPrime(int K){

int J;

for (J=2; J*J <= K; J++){
  if (Prime[J] == 1){
     if (K % J == 0)  {
        Prime[K] = 0;
        return 0;
     }
   }

}   

Prime[K] = 1; 
return 1;
}

This is my main.c

#include <stdio.h>
#include "defs.h"
#include "checkprime.c"

int Prime[MaxPrimes]; 

int main()
{ 
int UpperBound;
int N;
int *ba = &UpperBound;

printf("enter upper bound\n");
scanf("%d",ba);

Prime[2] = 1;

for (N = 3; N <= *ba; N+= 2){
  CheckPrime(N);
  if (Prime[N]== 1) printf("%d is a prime\n",N);
 }
}

And here is my minunit.c (test, which is implemented):

#undef NDEBUG
#ifndef _minunit_h
#define _minunit_h

#include <stdio.h>
#include <stdlib.h>

#define mu_suite_start() char *message = NULL

#define mu_assert(test, message) if (!(test)) { return message; }
#define mu_run_test(test) \                 
message = test(); tests_run++; if (message) return message;

#define RUN_TESTS(name) int main(int argc, char *argv[]) {\
argc = 1; \
    printf("----\nRUNNING: %s\n", argv[0]);\
    char *result = name();\
    if (result != 0) {\
        printf("FAILED: %s\n", result);\
    }\
    else {\
        printf("ALL TESTS PASSED\n");\
    }\
printf("Tests run: %d\n", tests_run);\
    exit(result != 0);\
}

int tests_run;

#endif

I found the minunit.c on the internet, and I don't know how to implement the test I want, and let it work. My goal is to make a simple test for my program.

Answer 1

And here is my minunit.c …

I presume you meant minunit.h. Given that, you could implement the test like mu_checkprime.c:

#include "checkprime.c"

int Prime[MaxPrimes]; 

static char *test_primes()
{
    mu_assert(CheckPrime(2) == 1,   "2 not found to be prime");
    mu_assert(CheckPrime(3) == 1,   "3 not found to be prime");
    mu_assert(CheckPrime(5) == 1,   "5 not found to be prime");
    mu_assert(CheckPrime(7) == 1,   "7 not found to be prime");
    mu_assert(CheckPrime(11) == 1, "11 not found to be prime");
    mu_assert(CheckPrime(13) == 1, "13 not found to be prime");
    return 0;
}

static char *test_composites()
{
    mu_assert(CheckPrime(1) == 0,   "1 found to be prime");
    mu_assert(CheckPrime(4) == 0,   "4 found to be prime");
    mu_assert(CheckPrime(6) == 0,   "6 found to be prime");
    mu_assert(CheckPrime(8) == 0,   "8 found to be prime");
    mu_assert(CheckPrime(9) == 0,   "9 found to be prime");
    mu_assert(CheckPrime(10) == 0, "10 found to be prime");
    mu_assert(CheckPrime(12) == 0, "12 found to be prime");
    mu_assert(CheckPrime(14) == 0, "14 found to be prime");
    return 0;
}

static char *all_tests()
{
     mu_suite_start();
     mu_run_test(test_primes);
     mu_run_test(test_composites);
     return 0;
}

RUN_TESTS(all_tests)

Answer 2

Ultimately, a test is nothing more than some code which exercises your code and checks your assumptions are true. When you're starting out, keep it simple. Instead of using a testing framework, start with just assert().

Here is how you can test CheckPrime().

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

void test_CheckPrime_primes() {
    int primes[] = {
        2, 3, 5, 7, 11, 13, 0
    };

    for( int idx = 0; primes[idx] != 0; idx++ ) {
        assert( CheckPrime(primes[idx]) );
    }
}

void test_CheckPrime_composites() {
    int composites[] = {
        1, 4, 6, 8, 9, 10, 12, 14, 0
    };

    for( int idx = 0; composites[idx] != 0; idx++ ) {
        assert( !CheckPrime(composites[idx]) );
    }
}

int main() {
    test_CheckPrime_primes();
    test_CheckPrime_composites();

    return 0;
}

This simple test program will reveal problems with using CheckPrime(). The two biggest are that it does not have a header file and Primes must be initialized by the caller. It will also allow you to learn what sort of assertions to write. For example, what happens with 0? 1? -1? INT_MAX? A candidate larger than your Primes array?

Once you've got the basics down and understand what testing is all about, assert() can be replaced with more informative asserts and a testing framework.