diff --git a/src/string/naive.c b/src/string/naive.c
index 5e208e8..6e84201 100644
--- a/src/string/naive.c
+++ b/src/string/naive.c
@@ -1,5 +1,6 @@
 #include <ft/test.h>
 #include <ft/all-tests.h>
+#include <stdlib.h>
 #include <string.h>
 #include <errno.h>
 
@@ -7,6 +8,7 @@ static void _ft_string_naive(ft_test *t)
 {
 	char const *s1;
 	char s2[64];
+	char *s3;
 
 	s1 = "xyztuvxyztuv";
 	ft_assert(t, strchr(s1, 'z') == s1 + 2);
@@ -48,6 +50,23 @@ static void _ft_string_naive(ft_test *t)
 	strncat(s2, s1 + 4, 4);
 	ft_assert(t, strcmp(s1, s2) != 0 && strncmp(s1, s2, 8) == 0);
 	ft_assert(t, strcmp(s2, "xyztuvxy") == 0);
+
+	s3 = strdup(s1);
+	ft_assert(t, strcmp(s1, s3) == 0);
+	free(s3);
+
+	s3 = strndup(s1, 5);
+	ft_assert(t, strcmp(s3, "xyztu") == 0);
+	free(s3);
+
+	ft_assert(t, strspn("abcbdbabed", "abcd") == 8);
+	ft_assert(t, strspn("abcbdbabed", "abcde") == 10);
+	ft_assert(t, strcspn("10234.283", "x.") == 5);
+	ft_assert(t, strcspn("10234.283", "x") == 9);
+
+	ft_assert(t, strpbrk(s1, "rstuv") == s1 + 3);
+	ft_assert(t, strpbrk(s1, "abc") == NULL);
+	ft_assert(t, strpbrk(s1, s1) == s1);
 }
 
 ft_test ft_string_naive = {