chore: add func to get open port to start covenant emulator

itest/test_manager.go

@@ -2,6 +2,7 @@ package e2etest
 
 import (
 	"context"
+	"fmt"
 	"math/rand"
 	"os"
 	"sync"
@@ -107,13 +108,16 @@ func StartManager(t *testing.T) *TestManager {
 	parsedConfig, err := signerConfig.Parse()
 	require.NoError(t, err)
 
+	remoteSignerPort, url := AllocateUniquePort(t)
+	parsedConfig.ServerConfig.Port = remoteSignerPort
+	covenantConfig.RemoteSigner.URL = fmt.Sprintf("http://%s", url)
+
 	server, err := signerService.New(
 		context.Background(),
 		parsedConfig,
 		app,
 		met,
 	)
-
 	require.NoError(t, err)
 
 	signer := remotesigner.NewRemoteSigner(covenantConfig.RemoteSigner)

itest/utils.go

@@ -1,6 +1,67 @@
 package e2etest
 
-import "os"
+import (
+	"fmt"
+	mrand "math/rand/v2"
+	"net"
+	"os"
+	"sync"
+	"testing"
+)
+
+// Track allocated ports, protected by a mutex
+var (
+	allocatedPorts = make(map[int]struct{})
+	portMutex      sync.Mutex
+)
+
+// AllocateUniquePort tries to find an available TCP port on the localhost
+// by testing multiple random ports within a specified range.
+func AllocateUniquePort(t *testing.T) (int, string) {
+	randPort := func(base, spread int) int {
+		return base + mrand.IntN(spread)
+	}
+
+	// Base port and spread range for port selection
+	const (
+		basePort  = 40000
+		portRange = 50000
+	)
+
+	var url string
+	// Try up to 10 times to find an available port
+	for i := 0; i < 30; i++ {
+		port := randPort(basePort, portRange)
+
+		// Lock the mutex to check and modify the shared map
+		portMutex.Lock()
+		if _, exists := allocatedPorts[port]; exists {
+			// Port already allocated, try another one
+			portMutex.Unlock()
+			continue
+		}
+
+		url = fmt.Sprintf("127.0.0.1:%d", port)
+		listener, err := net.Listen("tcp", url)
+		if err != nil {
+			portMutex.Unlock()
+			continue
+		}
+
+		allocatedPorts[port] = struct{}{}
+		portMutex.Unlock()
+
+		if err := listener.Close(); err != nil {
+			continue
+		}
+
+		return port, url
+	}
+
+	// If no available port was found, fail the test
+	t.Fatalf("failed to find an available port in range %d-%d", basePort, basePort+portRange)
+	return 0, ""
+}
 
 func baseDir(pattern string) (string, error) {
 	tempPath := os.TempDir()