diff --git a/.github/workflows/compile.yml b/.github/workflows/compile.yml
index badf1d0..6e097a3 100644
--- a/.github/workflows/compile.yml
+++ b/.github/workflows/compile.yml
@@ -51,9 +51,9 @@ jobs:
         run: make -C example/macOS
         if: runner.arch == 'ARM64'
   test:
-    needs: build
+    needs: formatting-check
     runs-on: ${{ matrix.os }}
-    timeout-minutes: 30
+    timeout-minutes: 3
     strategy:
       fail-fast: false
       # Can't expand the matrix due to the flakiness of the CI infra
@@ -73,4 +73,3 @@ jobs:
         run: make download_kernel
       - name: Unit Test
         run: make test
-        timeout-minutes: 10
diff --git a/Makefile b/Makefile
index 4197b2e..d0094fd 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-PUIPUI_LINUX_VERSION := 0.0.1
+PUIPUI_LINUX_VERSION := 1.0.3
 ARCH := $(shell uname -m)
 KERNEL_ARCH := $(shell echo $(ARCH) | sed -e s/arm64/aarch64/)
 KERNEL_TAR := puipui_linux_v$(PUIPUI_LINUX_VERSION)_$(KERNEL_ARCH).tar.gz
@@ -10,7 +10,7 @@ fmt:
 
 .PHONY: test
 test:
-	go test -p 1 -exec "go run $(PWD)/cmd/codesign" ./... -timeout 60s -v
+	go test -p 1 -exec "go run $(PWD)/cmd/codesign" ./... -timeout 2m -v
 
 .PHONY: test/run
 test/run:
diff --git a/virtualization_test.go b/virtualization_test.go
index f42d8dd..d56a736 100644
--- a/virtualization_test.go
+++ b/virtualization_test.go
@@ -3,6 +3,8 @@ package vz_test
 import (
 	"errors"
 	"fmt"
+	"math"
+	"net"
 	"os"
 	"runtime"
 	"syscall"
@@ -111,15 +113,30 @@ func (c *Container) NewSession(t *testing.T) *ssh.Session {
 	return sshSession
 }
 
+func getFreePort() (int, error) {
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		return 0, err
+	}
+	defer l.Close()
+	return l.Addr().(*net.TCPAddr).Port, nil
+}
+
 func newVirtualizationMachine(
 	t *testing.T,
 	configs ...func(*vz.VirtualMachineConfiguration) error,
 ) *Container {
+	port, err := getFreePort()
+	if err != nil {
+		t.Fatalf("failed to resolve free tcp addr: %v", err)
+	}
+
 	vmlinuz := "./testdata/Image"
 	initramfs := "./testdata/initramfs.cpio.gz"
+	cmdline := fmt.Sprintf("console=hvc0 vsock_port=%d", port)
 	bootLoader, err := vz.NewLinuxBootLoader(
 		vmlinuz,
-		vz.WithCommandLine("console=hvc0"),
+		vz.WithCommandLine(cmdline),
 		vz.WithInitrd(initramfs),
 	)
 	if err != nil {
@@ -172,28 +189,52 @@ func newVirtualizationMachine(
 		time.Sleep(5 * time.Second)
 	}
 
+	const max = 5
 RETRY:
 	for i := 1; ; i++ {
-		conn, err := socketDevice.Connect(2222)
+		conn, err := socketDevice.Connect(uint32(port))
 		if err != nil {
 			var nserr *vz.NSError
-			if !errors.As(err, &nserr) || i > 5 {
+			if !errors.As(err, &nserr) || i > max {
 				t.Fatal(err)
 			}
 			if nserr.Code == int(syscall.ECONNRESET) {
 				t.Logf("retry vsock connect: %d", i)
-				time.Sleep(time.Second)
+				time.Sleep(backOffDelay(i))
 				continue RETRY
 			}
 			t.Fatalf("failed to connect vsock: %v", err)
 		}
 
+		t.Log("setup ssh client in container")
+
+		initialized := make(chan struct{})
+		retry := make(chan struct{})
+		go func() {
+			select {
+			case <-initialized:
+			case <-time.After(5 * time.Second):
+				close(retry)
+				t.Log("closed", conn.Close())
+			}
+		}()
+
 		sshClient, err := testhelper.NewSshClient(conn, ":22", sshConfig)
 		if err != nil {
+			select {
+			case <-retry:
+				t.Log("retry because ssh handshake has been failed")
+				continue RETRY
+			default:
+			}
 			conn.Close()
 			t.Fatalf("failed to create a new ssh client: %v", err)
 		}
 
+		close(initialized)
+
+		t.Logf("container setup done")
+
 		return &Container{
 			VirtualMachine: vm,
 			Client:         sshClient,
@@ -201,6 +242,12 @@ RETRY:
 	}
 }
 
+func backOffDelay(retryAttempts int) time.Duration {
+	factor := 0.5
+	delay := math.Exp2(float64(retryAttempts)) * factor
+	return time.Duration(math.Min(delay, 10)) * time.Second
+}
+
 func waitState(t *testing.T, wait time.Duration, vm *vz.VirtualMachine, want vz.VirtualMachineState) {
 	t.Helper()
 	select {