range in C

range.c

int* range(int start, int end) {
    int len;
    if (start <= end) {
        len = end - start + 1;
    } else {
        len = start - end + 1;
    }
    int* array = malloc(sizeof(int) * len);
    if (start == end){
        array[0] = start;
    } else if (start < end) {
        int i = 0;
        while (i < len) {
            array[i] = start;
            start++;
            i++;
        }
    } else {
        int i = 0;
        while (i < len) {
            array[i] = start;
            start--;
            i++;
        }
    }
    return array;
}

range_test.c

#include <check.h>
#include "utils.h"

// Function prototypes
Suite* swap_suite(void);

START_TEST(test_range) {
    int* array = range(0, 10);

    ck_assert_int_eq(array[0],0);
    ck_assert_int_eq(array[1],1);
    ck_assert_int_eq(array[9],9);
    ck_assert_int_eq(array[10],10);

    int* array2 = range(3, 7);
    ck_assert_int_eq(array2[0],3);
    ck_assert_int_eq(array2[4],7);

    int* array3 = range(-3, 1);
    ck_assert_int_eq(array3[0],-3);
    ck_assert_int_eq(array3[1],-2);
    ck_assert_int_eq(array3[2],-1);
    ck_assert_int_eq(array3[3],0);
    ck_assert_int_eq(array3[4],1);

    int* array4 = range(1, 1);
    ck_assert_int_eq(array4[0],1);

    int* array5 = range(0, -3); // 0 -1 -2 -3 
    ck_assert_int_eq(array5[0], 0);
    ck_assert_int_eq(array5[1], -1);
    ck_assert_int_eq(array5[2], -2);
    ck_assert_int_eq(array5[3], -3);
}
END_TEST

// Suite setup
Suite* swap_suite(void) {
    Suite *s;
    TCase *tc_core;

    s = suite_create("utils");

    /* Core test case */
    tc_core = tcase_create("Core");

    tcase_add_test(tc_core, test_is_num_in_stack);
    tcase_add_test(tc_core, test_range);

    suite_add_tcase(s, tc_core);

    return s;
}

// Main function to run the test suite
int main(void) {
    int number_failed;
    Suite *s;
    SRunner *sr;

    s = swap_suite();
    sr = srunner_create(s);

    srunner_run_all(sr, CK_VERBOSE);
    number_failed = srunner_ntests_failed(sr);
    srunner_free(sr);
    return (number_failed == 0) ? EXIT_SUCCESS : EXIT_FAILURE;
}

cc utils.c utils_test.c -I /opt/homebrew/include -lcheck -L/opt/homebrew/lib -o utils_test

./utils_test
Running suite(s): utils
100%: Checks: 2, Failures: 0, Errors: 0
utils_test.c:57:P:Core:test_range:0: Passed