test(random): add unit tests for random behavior

- Added unit tests to cover random string generation and error handling.
- Introduced Random interface and random struct for better abstraction.
- Updated server, session, and interaction packages to require Random interface for dependency injection.

server/server.go

@@ -10,6 +10,7 @@ import (
 	"tunnel_pls/internal/config"
 	"tunnel_pls/internal/grpc/client"
 	"tunnel_pls/internal/port"
+	"tunnel_pls/internal/random"
 	"tunnel_pls/internal/registry"
 	"tunnel_pls/session"
 
@@ -21,6 +22,7 @@ type Server interface {
 	Close() error
 }
 type server struct {
+	randomizer      random.Random
 	config          config.Config
 	sshPort         string
 	sshListener     net.Listener
@@ -30,13 +32,14 @@ type server struct {
 	portRegistry    port.Port
 }
 
-func New(config config.Config, sshConfig *ssh.ServerConfig, sessionRegistry registry.Registry, grpcClient client.Client, portRegistry port.Port, sshPort string) (Server, error) {
+func New(randomizer random.Random, config config.Config, sshConfig *ssh.ServerConfig, sessionRegistry registry.Registry, grpcClient client.Client, portRegistry port.Port, sshPort string) (Server, error) {
 	listener, err := net.Listen("tcp", fmt.Sprintf(":%s", sshPort))
 	if err != nil {
 		return nil, err
 	}
 
 	return &server{
+		randomizer:      randomizer,
 		config:          config,
 		sshPort:         sshPort,
 		sshListener:     listener,
@@ -95,7 +98,7 @@ func (s *server) handleConnection(conn net.Conn) {
 		cancel()
 	}
 	log.Println("SSH connection established:", sshConn.User())
-	sshSession := session.New(s.config, sshConn, forwardingReqs, chans, s.sessionRegistry, s.portRegistry, user)
+	sshSession := session.New(s.randomizer, s.config, sshConn, forwardingReqs, chans, s.sessionRegistry, s.portRegistry, user)
 	err = sshSession.Start()
 	if err != nil {
 		log.Printf("SSH session ended with error: %v", err)