tstest/integration: stop skipping five tests on Windows

Updates #20750

Signed-off-by: Yaruk Asghar <yaruk@tailscale.com>

tstest/integration/integration.go

@@ -597,6 +597,8 @@ type TestNode struct {
 	allowUpdates bool
 	tunMode      bool // TUN rather than userspace networking
 
+	svcStarted bool // whether this node has started its Windows service before
+
 	mu        sync.Mutex
 	onLogLine []func([]byte)
 	lc        *local.Client
@@ -887,6 +889,10 @@ type waitResult struct {
 		d.Process.Kill()
 		<-done
 	}
+	if d.svc != nil {
+		// Uninstall so the node can start a fresh service; its state dir persists.
+		d.svc.uninstallService()
+	}
 }
 
 // awaitTailscaledRunnable tries to run `tailscaled --version` until it

tstest/integration/integration_test.go

@@ -206,9 +206,6 @@ func TestExpectedFeaturesLinked(t *testing.T) {
 }
 
 func TestCollectPanic(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		t.Skip("has a Windows panic-capture race; see #20443")
-	}
 	tstest.Parallel(t)
 	env := NewTestEnv(t)
 	n := NewTestNode(t, env)
@@ -848,16 +845,14 @@ func(control *testcontrol.Server) {
 }
 
 func TestConfigFileAuthKey(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		t.Skip("--config is unsupported by the Windows service; see #20871")
-	}
 	t.Parallel()
 	const authKey = "opensesame"
 	env := NewTestEnv(t, ConfigureControl(func(control *testcontrol.Server) {
 		control.RequireAuthKey = authKey
 	}))
 
-	n1 := NewTestNode(t, env)
+	// A userspace node, because the Windows service can't be passed --config.
+	n1 := NewTestNode(t, env, TUNMode(false))
 	n1.configFile = filepath.Join(n1.dir, "config.json")
 	authKeyFile := filepath.Join(n1.dir, "my-auth-key")
 	must.Do(os.WriteFile(authKeyFile, fmt.Appendf(nil, "%s\n", authKey), 0666))
@@ -1274,9 +1269,6 @@ func TestC2NPingRequest(t *testing.T) {
 // Issue 2434: when "down" (WantRunning false), tailscaled shouldn't
 // be connected to control.
 func TestNoControlConnWhenDown(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		t.Skip("restarting the daemon with preserved state needs harness support; see #20750")
-	}
 	tstest.Parallel(t)
 	env := NewTestEnv(t)
 	n1 := NewTestNode(t, env)
@@ -1644,9 +1636,6 @@ func TestAutoUpdateDefaults_cap(t *testing.T) { testAutoUpdateDefaults(t, true)
 // useCap is whether to use NodeAttrDefaultAutoUpdate (as opposed to the old
 // DeprecatedDefaultAutoUpdate top-level MapResponse field).
 func testAutoUpdateDefaults(t *testing.T, useCap bool) {
-	if runtime.GOOS == "windows" {
-		t.Skip("multiple nodes need the userspace-peer harness; see #20711")
-	}
 	t.Cleanup(feature.HookCanAutoUpdate.SetForTest(func() bool { return true }))
 
 	env := NewTestEnv(t)
@@ -2128,9 +2117,6 @@ func TestNetstackUDPLoopback(t *testing.T) {
 }
 
 func TestEncryptStateMigration(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		t.Skip("--encrypt-state is unsupported by the Windows service; see #20872")
-	}
 	if !hostinfo.New().TPM.Present() {
 		t.Skip("TPM not available")
 	}
@@ -2139,7 +2125,8 @@ func TestEncryptStateMigration(t *testing.T) {
 	}
 	tstest.Parallel(t)
 	env := NewTestEnv(t)
-	n := NewTestNode(t, env)
+	// A userspace node, because runNode reads the state file from the test's own dir.
+	n := NewTestNode(t, env, TUNMode(false))
 
 	runNode := func(t *testing.T, wantStateKeys []string) {
 		t.Helper()

tstest/integration/service_notwindows.go

@@ -16,3 +16,7 @@ func (n *TestNode) startWindowsServiceDaemon() *Daemon {
 func (n *TestNode) stopService() {
 	n.env.t.Fatal("Windows service daemon is only supported on Windows")
 }
+
+func (n *TestNode) uninstallService() {
+	n.env.t.Fatal("Windows service daemon is only supported on Windows")
+}

tstest/integration/service_windows.go

@@ -40,7 +40,11 @@ func (n *TestNode) startWindowsServiceDaemon() *Daemon {
 		t.Fatal("existing Tailscale service found; run only on a disposable/CI machine")
 	}
 
-	n.cleanupServiceState()
+	// Only on a node's first start: a restart keeps its state, and so its identity.
+	if !n.svcStarted {
+		n.cleanupServiceState()
+	}
+	n.svcStarted = true
 	stageWintun(t, filepath.Dir(n.env.daemon))
 	n.writeServiceEnvFile()
 
@@ -48,8 +52,7 @@ func (n *TestNode) startWindowsServiceDaemon() *Daemon {
 		t.Fatalf("install-system-daemon: %v\n%s", err, out)
 	}
 	var proc *os.Process
-	// Teardown: stop, wait for the process to exit so it releases the files below,
-	// uninstall, then wipe state for the next test.
+	// Safety net for tests that never call MustCleanShutdown, plus the final state wipe.
 	t.Cleanup(func() {
 		n.stopService()
 		if proc != nil {