feat: 增强桌面启动失败提示与测试覆盖

backend/cmd/desktop/dialog_linux_test.go

@@ -0,0 +1,61 @@
+//go:build linux
+
+package main
+
+import "testing"
+
+func TestLinuxStartupChannelsPriorityAndArguments(t *testing.T) {
+	t.Setenv("DISPLAY", ":0")
+	t.Setenv("DBUS_SESSION_BUS_ADDRESS", "unix:path=/tmp/dbus")
+	runner := &fakeCommandRunner{paths: map[string]bool{
+		"notify-send": true,
+		"kdialog":     true,
+		"zenity":      true,
+		"xmessage":    true,
+	}}
+
+	channels := platformStartupChannels(runner)
+	if len(channels) != 5 {
+		t.Fatalf("Linux 应有 5 个 UI 通道，实际: %d", len(channels))
+	}
+
+	req := promptRequest{title: "Nex 启动失败", message: "端口被占用"}
+	for _, channel := range channels {
+		if err := channel.available(); err != nil {
+			t.Fatalf("通道 %s 应可用: %v", channel.name, err)
+		}
+		if err := channel.run(req); err != nil {
+			t.Fatalf("通道 %s 执行失败: %v", channel.name, err)
+		}
+	}
+
+	wantNames := []string{"notify-send", "kdialog", "zenity", "kdialog", "xmessage"}
+	for i, want := range wantNames {
+		if got := runner.calls[i].name; got != want {
+			t.Fatalf("第 %d 个命令 = %s, want %s", i, got, want)
+		}
+	}
+	if got := runner.calls[0].args; len(got) < 2 || got[0] != "-u" || got[1] != "critical" {
+		t.Fatalf("notify-send 应使用 critical 参数，实际: %#v", got)
+	}
+	if got := runner.calls[1].args; len(got) < 3 || got[2] != "--passivepopup" {
+		t.Fatalf("kdialog 第一跳应使用 passivepopup，实际: %#v", got)
+	}
+	if got := runner.calls[2].args; len(got) < 1 || got[0] != "--error" {
+		t.Fatalf("zenity 应使用 --error，实际: %#v", got)
+	}
+	if got := runner.calls[4].args; len(got) < 1 || got[0] != "-center" {
+		t.Fatalf("xmessage 应居中显示，实际: %#v", got)
+	}
+}
+
+func TestLinuxNotifySendRequiresDBus(t *testing.T) {
+	t.Setenv("DISPLAY", ":0")
+	t.Setenv("DBUS_SESSION_BUS_ADDRESS", "")
+	runner := &fakeCommandRunner{paths: map[string]bool{"notify-send": true}}
+
+	channels := platformStartupChannels(runner)
+	if err := channels[0].available(); err == nil {
+		t.Fatal("notify-send 缺少 DBus session bus 时应不可用")
+	}
+}