diff --git a/src/utils/myrsa.rs b/src/utils/myrsa.rs
index c5735dd..675c7c9 100644
--- a/src/utils/myrsa.rs
+++ b/src/utils/myrsa.rs
@@ -109,7 +109,7 @@ pub fn rsa_decrypt(privkey: &RsaPrivateKey, cipherd: &[u8]) -> Result<Vec<u8>> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::utils::test_utils::generate_info;
+    use crate::utils::{ip_to_string, net_bit_len_to_mask, test_utils::generate_info};
 
     fn generate_key() {
         if std::fs::File::open(".data/id_rsa").is_ok() {
@@ -144,4 +144,12 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn test_net_bit_to_ip() {
+        assert_eq!(ip_to_string(net_bit_len_to_mask(8)), "255.0.0.0");
+        assert_eq!(ip_to_string(net_bit_len_to_mask(16)), "255.255.0.0");
+        assert_eq!(ip_to_string(net_bit_len_to_mask(24)), "255.255.255.0");
+        assert_eq!(ip_to_string(net_bit_len_to_mask(32)), "255.255.255.255");
+    }
 }