C test to check if a number is prime

solution.c

#include <stdbool.h>

#ifndef Solution_INCLUDED
#define Solution_INCLUDED

bool IsPrime(int input);

#endif


#include "solution.h"
#include <stdbool.h>

bool IsPrime(int input)
{
    // those are NOT prime by definition
    if (input < 1) {
        return false;
    }
    
    // those are prime by definition
    // 1 of course
    // 2 is the only even number that is also prime
    if (input == 1 || input == 2) {
        return true;
    }

    // even number can't be prime
    if (input % 2 == 0) {
        return false;
    }

    // loop over all the odd number
    // from 3 up to 1/2 of input
    for (int divider = 3; divider < input / 2; divider+=2) {
        if (input % divider == 0) {
            // if input is divisible by divider
            // it means that input is NOT prime
            return false;
        }
    }

    // if we reach this point
    // it means that we couldn't find
    // another divider rather than 1 and input itself
    // so input IS prime
    return true;
}

solution.h

#include <stdbool.h>

#ifndef Solution_INCLUDED
#define Solution_INCLUDED

bool IsPrime(int input);

#endif

test.c

#include "solution.h"
#include "unity.h"
#include <stdbool.h>

void setUp(void)
{
}

void tearDown(void)
{
}

void test1(void)
{
    int input = 3;
    bool expected = true;

    bool output = IsPrime(input);

    TEST_ASSERT_EQUAL(expected, output);
}

void test2(void)
{
    int input = 4;
    bool expected = false;

    bool output = IsPrime(input);

    TEST_ASSERT_EQUAL(expected, output);
}

void test3(void)
{
    int input = 7;
    bool expected = true;

    bool output = IsPrime(input);

    TEST_ASSERT_EQUAL(expected, output);
}

void test4(void)
{
    int input = 21;
    bool expected = false;

    bool output = IsPrime(input);

    TEST_ASSERT_EQUAL(expected, output);
}