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.

internal/random/random.go

@@ -1,12 +1,35 @@
 package random
 
-import "crypto/rand"
+import (
+	"crypto/rand"
+	"fmt"
+	"io"
+)
 
-func GenerateRandomString(length int) (string, error) {
+var (
+	ErrInvalidLength = fmt.Errorf("invalid length")
+)
+
+type Random interface {
+	String(length int) (string, error)
+}
+
+type random struct {
+	reader io.Reader
+}
+
+func New() Random {
+	return &random{reader: rand.Reader}
+}
+
+func (ran *random) String(length int) (string, error) {
+	if length < 0 {
+		return "", ErrInvalidLength
+	}
 	const charset = "abcdefghijklmnopqrstuvwxyz0123456789"
 	b := make([]byte, length)
 
-	if _, err := rand.Read(b); err != nil {
+	if _, err := ran.reader.Read(b); err != nil {
 		return "", err
 	}
 

internal/random/random_test.go

@@ -0,0 +1,61 @@
+package random
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+)
+
+type brainrotReader struct {
+	err error
+}
+
+func (f *brainrotReader) Read(p []byte) (int, error) {
+	return 0, f.err
+}
+
+func TestRandom_String(t *testing.T) {
+	tests := []struct {
+		name    string
+		length  int
+		wantErr bool
+	}{
+		{"ValidLengthZero", 0, false},
+		{"ValidPositiveLength", 10, false},
+		{"NegativeLength", -1, true},
+		{"VeryLargeLength", 1_000_000, false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			randomizer := New()
+
+			result, err := randomizer.String(tt.length)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("String() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+
+			if !tt.wantErr && len(result) != tt.length {
+				t.Errorf("String() length = %v, want %v", len(result), tt.length)
+			}
+		})
+	}
+}
+
+func TestRandomWithFailingReader_String(t *testing.T) {
+	var randomizer Random
+	var errBrainrot = fmt.Errorf("you are not sigma enough")
+	randomizer = &random{reader: &brainrotReader{err: errBrainrot}}
+	t.Run("test failing reader", func(t *testing.T) {
+		result, err := randomizer.String(20)
+		if !errors.Is(err, errBrainrot) {
+			t.Errorf("String() error = %v, wantErr %v", err, errBrainrot)
+			return
+		}
+
+		if result != "" {
+			t.Errorf("String() result = %v, want an empty string due to error", result)
+		}
+	})
+}

main.go

@@ -15,6 +15,7 @@ import (
 	"tunnel_pls/internal/grpc/client"
 	"tunnel_pls/internal/key"
 	"tunnel_pls/internal/port"
+	"tunnel_pls/internal/random"
 	"tunnel_pls/internal/registry"
 	"tunnel_pls/internal/transport"
 	"tunnel_pls/internal/version"
@@ -134,10 +135,10 @@ func main() {
 		log.Fatalf("Failed to initialize port manager: %s", err)
 		return
 	}
-
+	randomizer := random.New()
 	var app server.Server
 	go func() {
-		app, err = server.New(conf, sshConfig, sessionRegistry, grpcClient, portManager, conf.SSHPort())
+		app, err = server.New(randomizer, conf, sshConfig, sessionRegistry, grpcClient, portManager, conf.SSHPort())
 		if err != nil {
 			errChan <- fmt.Errorf("failed to start server: %s", err)
 			return

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)

session/interaction/interaction.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"log"
 	"tunnel_pls/internal/config"
+	"tunnel_pls/internal/random"
 	"tunnel_pls/session/slug"
 	"tunnel_pls/types"
 
@@ -39,6 +40,7 @@ type Forwarder interface {
 
 type CloseFunc func() error
 type interaction struct {
+	randomizer      random.Random
 	config          config.Config
 	channel         ssh.Channel
 	slug            slug.Slug
@@ -76,9 +78,10 @@ func (i *interaction) SetWH(w, h int) {
 	}
 }
 
-func New(config config.Config, slug slug.Slug, forwarder Forwarder, sessionRegistry SessionRegistry, user string, closeFunc CloseFunc) Interaction {
+func New(randomizer random.Random, config config.Config, slug slug.Slug, forwarder Forwarder, sessionRegistry SessionRegistry, user string, closeFunc CloseFunc) Interaction {
 	ctx, cancel := context.WithCancel(context.Background())
 	return &interaction{
+		randomizer:      randomizer,
 		config:          config,
 		channel:         nil,
 		slug:            slug,
@@ -210,6 +213,7 @@ func (i *interaction) Start() {
 	ti.Width = 50
 
 	m := &model{
+		randomizer:  i.randomizer,
 		domain:      i.config.Domain(),
 		protocol:    protocol,
 		tunnelType:  tunnelType,

session/interaction/model.go

@@ -3,6 +3,7 @@ package interaction
 import (
 	"fmt"
 	"time"
+	"tunnel_pls/internal/random"
 	"tunnel_pls/types"
 
 	"github.com/charmbracelet/bubbles/help"
@@ -22,6 +23,7 @@ func (i commandItem) Title() string       { return i.name }
 func (i commandItem) Description() string { return i.desc }
 
 type model struct {
+	randomizer        random.Random
 	domain            string
 	protocol          string
 	tunnelType        types.TunnelType

session/interaction/slug.go

@@ -3,7 +3,6 @@ package interaction
 import (
 	"fmt"
 	"strings"
-	"tunnel_pls/internal/random"
 	"tunnel_pls/types"
 
 	"github.com/charmbracelet/bubbles/key"
@@ -47,7 +46,7 @@ func (m *model) slugUpdate(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 		return m, tea.Batch(tea.ClearScreen, textinput.Blink)
 	default:
 		if key.Matches(msg, m.keymap.random) {
-			newSubdomain, err := random.GenerateRandomString(20)
+			newSubdomain, err := m.randomizer.String(20)
 			if err != nil {
 				return m, cmd
 			}

session/session.go

@@ -37,6 +37,7 @@ type Session interface {
 }
 
 type session struct {
+	randomizer  random.Random
 	config      config.Config
 	initialReq  <-chan *ssh.Request
 	sshChan     <-chan ssh.NewChannel
@@ -49,13 +50,14 @@ type session struct {
 
 var blockedReservedPorts = []uint16{1080, 1433, 1521, 1900, 2049, 3306, 3389, 5432, 5900, 6379, 8080, 8443, 9000, 9200, 27017}
 
-func New(config config.Config, conn *ssh.ServerConn, initialReq <-chan *ssh.Request, sshChan <-chan ssh.NewChannel, sessionRegistry registry.Registry, portRegistry portUtil.Port, user string) Session {
+func New(randomizer random.Random, config config.Config, conn *ssh.ServerConn, initialReq <-chan *ssh.Request, sshChan <-chan ssh.NewChannel, sessionRegistry registry.Registry, portRegistry portUtil.Port, user string) Session {
 	slugManager := slug.New()
 	forwarderManager := forwarder.New(config, slugManager, conn)
 	lifecycleManager := lifecycle.New(conn, forwarderManager, slugManager, portRegistry, sessionRegistry, user)
-	interactionManager := interaction.New(config, slugManager, forwarderManager, sessionRegistry, user, lifecycleManager.Close)
+	interactionManager := interaction.New(randomizer, config, slugManager, forwarderManager, sessionRegistry, user, lifecycleManager.Close)
 
 	return &session{
+		randomizer:  randomizer,
 		config:      config,
 		initialReq:  initialReq,
 		sshChan:     sshChan,
@@ -346,7 +348,7 @@ func (s *session) HandleTCPIPForward(req *ssh.Request) error {
 }
 
 func (s *session) HandleHTTPForward(req *ssh.Request, portToBind uint16) error {
-	randomString, err := random.GenerateRandomString(20)
+	randomString, err := s.randomizer.String(20)
 	if err != nil {
 		return s.denyForwardingRequest(req, nil, nil, fmt.Sprintf("Failed to create slug: %s", err))
 	}