trying to find out what I dont understand

test_arena_allocator.c

@@ -1,5 +1,6 @@
 #include <criterion/criterion.h>
 #include "cig.h"
+#include <stdio.h>
 
 Test(arena_allocator, repeated_allocations) {
     arena_allocator_t aalloc = arena_allocator_create();
@@ -16,4 +17,25 @@ Test(arena_allocator, repeated_allocations) {
     cr_assert_eq(aalloc.total_allocated, 0);
 }
 
+Test(arena_allocator, alignment) {
+    arena_allocator_t aalloc = arena_allocator_create();
+
+    for ( int i = 0; i < 10; i++ ) with_arena(&aalloc, allocator) {
+        allocator_alloc(allocator, 1000);
+    }
+
+	with_arena(&aalloc, allocator) {
+		size_t prev_addr = 0;
+		prev_addr = ~prev_addr;
+		for (int i = 0; i < 1001; i++) {
+			size_t addr = (size_t)allocator_alloc(allocator, 1);
+			cr_assert_neq(addr, prev_addr);
+			cr_assert_eq(addr % MAX_ALIGN, 0);
+		}
+	}
+	arena_allocator_reset(&aalloc);
+	fprintf(stderr, "%zu\n", aalloc.total_allocated);
+    cr_assert_eq(aalloc.total_allocated, MAX_ALIGN *  1000 + 1);
+}
+
 // TODO somehow test reallocations