diff --git a/ft_substr_test.c b/ft_substr_test.c
new file mode 100644
index 0000000..2e513dc
--- /dev/null
+++ b/ft_substr_test.c
@@ -0,0 +1,76 @@
+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   ft_substr_test.c                                   :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: lalgarra <lalgarra@student.42madrid.com>   +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2025/10/08 18:44:25 by lalgarra          #+#    #+#             */
+/*   Updated: 2025/10/08 19:17:14 by lalgarra         ###   ########.fr       */
+/*                                                                            */
+/* ************************************************************************** */
+
+
+#include "libft.h"
+#include <stdio.h>
+#include <string.h>
+
+static void	test(char *prefix, char buff[], unsigned int start, size_t len)
+{
+	char	*res;
+	int		fd;
+
+	fd = STDOUT_FILENO;
+	ft_putstr_fd(prefix, fd);
+	ft_putstr_fd("buff:[", fd);
+	ft_putstr_fd(buff, fd);
+	ft_putstr_fd("], start:[", fd);
+	ft_putnbr_fd(start, fd);
+	ft_putstr_fd("], len:[", fd);
+	ft_putnbr_fd(len, fd);
+	res = ft_substr(buff, start, len);
+	ft_putstr_fd("], result:[", fd);
+	if (res == NULL)
+		ft_putstr_fd("-NULL-", fd);
+	else
+		ft_putstr_fd(res, fd);
+	free(res);
+	ft_putendl_fd("]", fd);
+}
+
+static void	do_test1(void)
+{
+	test("test 1: ", "Lorem ipsum", 0, 10);
+}
+
+static void	do_test2(void)
+{
+	test("test 2: ", "Lorem ipsum", 7, 10);
+}
+
+static void	do_test3(void)
+{
+	test("test 3: ", "Lorem ipsum", 12, 10);
+}
+
+/*
+static void	zero(char buff[])
+{
+	ft_bzero(buff, 128);
+}
+
+static void	do_test2(char buff[])
+{
+	zero(buff);
+	ft_strlcpy(buff, "+-50", 5);
+}
+*/
+int	main(void)
+{
+	//char	buff[128];
+
+	do_test1();
+	do_test2();
+	do_test3();
+	return (0);
+}