test(mem-alloc): add realloc rejection tests

Verify realloc correctly rejects aligned allocations and
still works for normal allocations.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: lum1n0us

tests/unit/mem-alloc/mem_alloc_test.c

@@ -91,3 +91,60 @@ test_aligned_alloc_valid_alignments(void **state)
 
     mem_allocator_destroy(allocator);
 }
+
+/* Test: Realloc rejects aligned allocations */
+static void
+test_realloc_rejects_aligned(void **state)
+{
+    mem_allocator_t allocator;
+    char heap_buf[64 * 1024];
+    void *ptr, *new_ptr;
+
+    allocator = mem_allocator_create(heap_buf, sizeof(heap_buf));
+    assert_non_null(allocator);
+
+    /* Allocate aligned */
+    ptr = mem_allocator_malloc_aligned(allocator, 128, 64);
+    assert_non_null(ptr);
+    assert_true(is_aligned_allocation(ptr));
+
+    /* Realloc should reject aligned allocation */
+    new_ptr = mem_allocator_realloc(allocator, ptr, 256);
+    assert_null(new_ptr);
+
+    /* Original pointer should still be valid - free it */
+    mem_allocator_free(allocator, ptr);
+
+    mem_allocator_destroy(allocator);
+}
+
+/* Test: Realloc still works for normal allocations */
+static void
+test_normal_realloc_works(void **state)
+{
+    mem_allocator_t allocator;
+    char heap_buf[64 * 1024];
+    void *ptr, *new_ptr;
+
+    allocator = mem_allocator_create(heap_buf, sizeof(heap_buf));
+    assert_non_null(allocator);
+
+    /* Allocate normal */
+    ptr = mem_allocator_malloc(allocator, 128);
+    assert_non_null(ptr);
+
+    /* Write some data */
+    memset(ptr, 0xAB, 128);
+
+    /* Realloc should work */
+    new_ptr = mem_allocator_realloc(allocator, ptr, 256);
+    assert_non_null(new_ptr);
+
+    /* Data should be preserved */
+    for (int i = 0; i < 128; i++) {
+        assert_int_equal(((unsigned char *)new_ptr)[i], 0xAB);
+    }
+
+    mem_allocator_free(allocator, new_ptr);
+    mem_allocator_destroy(allocator);
+}

tests/unit/mem-alloc/test_runner.c

@@ -18,6 +18,8 @@ main(void)
     const struct CMUnitTest tests[] = {
         cmocka_unit_test(test_normal_alloc_basic),
         cmocka_unit_test(test_aligned_alloc_valid_alignments),
+        cmocka_unit_test(test_realloc_rejects_aligned),
+        cmocka_unit_test(test_normal_realloc_works),
     };
 
     return cmocka_run_group_tests(tests, NULL, NULL);