test: add and update a few tests

object-test/trees.c

@@ -32,7 +32,7 @@ int main(void)
 	b_dict_iterator it;
 	b_dict_foreach(&it, dict)
 	{
-		printf("item %zu: %s=%d\n", it.i, it.key,
+		printf("item %zu: %s=%d\n", it.i, b_string_ptr(it.key),
 		       b_number_get_int(B_NUMBER(it.value)));
 	}