tests/tests_gzlib_gz_intmax.c

#include "unity/unity.h"
#include "zlib.h"

#include <limits.h>
#include <stdint.h>

/* Forward declaration of the internal function under test. */
unsigned gz_intmax(void);

void setUp(void) {
    /* Setup code here, or leave empty */
}

void tearDown(void) {
    /* Cleanup code here, or leave empty */
}

/* Helper to compute expected INT_MAX using bit width (portable across int models). */
static unsigned expected_intmax_by_bits(void) {
    /* Compute 2^(sizeof(int)*CHAR_BIT - 1) - 1 in a wide type, then cast. */
    unsigned bits = (unsigned)(sizeof(int) * CHAR_BIT);
    /* bits is at least 16 by the C standard */
    unsigned long long one = 1ULL;
    unsigned long long max_val = (one << (bits - 1)) - 1ULL;
    return (unsigned)max_val;
}

void test_gz_intmax_equals_INT_MAX(void) {
    unsigned got = gz_intmax();
    TEST_ASSERT_EQUAL_UINT((unsigned)INT_MAX, got);
}

void test_gz_intmax_matches_bit_calculation(void) {
    unsigned got = gz_intmax();
    unsigned expected = expected_intmax_by_bits();
    TEST_ASSERT_EQUAL_UINT(expected, got);
}

void test_gz_intmax_is_consistent_across_calls(void) {
    unsigned a = gz_intmax();
    unsigned b = gz_intmax();
    unsigned c = gz_intmax();
    TEST_ASSERT_EQUAL_UINT(a, b);
    TEST_ASSERT_EQUAL_UINT(b, c);
}

void test_gz_intmax_basic_properties(void) {
    unsigned v = gz_intmax();

    /* It should be positive and not exceed UINT_MAX. */
    TEST_ASSERT_TRUE(v > 0);
    TEST_ASSERT_TRUE(v <= (unsigned)UINT_MAX);

    /* It should not be equal to UINT_MAX (since INT_MAX < UINT_MAX on all sane platforms). */
    TEST_ASSERT_TRUE(v != (unsigned)UINT_MAX);

    /* Adding 1 should increase the value without wrapping. */
    unsigned v_plus_1 = v + 1u;
    TEST_ASSERT_TRUE(v_plus_1 > v);
}

int main(void) {
    UNITY_BEGIN();
    RUN_TEST(test_gz_intmax_equals_INT_MAX);
    RUN_TEST(test_gz_intmax_matches_bit_calculation);
    RUN_TEST(test_gz_intmax_is_consistent_across_calls);
    RUN_TEST(test_gz_intmax_basic_properties);
    return UNITY_END();
}