test(client): L1 数值格式化纯函数单测 + 从 widget 抽出(支柱3)

- lib/util/format.dart:抽出 formatSpeed/formatDuration(原私有于 connect_page
  _speed / connect_button _fmt,混在 widget 里没法单测)
- connect_page/connect_button 改用公共纯函数(渲染输出不变)
- test/unit/format_test.dart:10 用例覆盖速率 B/s→GB/s 各单位边界 +
  时长 HH:MM:SS 补零/小时不封顶/取模 60
- 验证:format 10 + widget 8 全过、analyze 无 error/warning

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/lib/screens/connect_page.dart

@@ -4,6 +4,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../bridge/vpn_bridge.dart';
 import '../core/responsive/form_factor.dart';
+import '../util/format.dart';
 import '../l10n/app_text.dart';
 import '../models/node.dart';
 import '../pangolin_theme.dart';
@@ -33,8 +34,8 @@ class ConnectPage extends ConsumerWidget {
     final isFree = ref.watch(isFreePlanProvider);
     final quota = ref.watch(quotaProvider);
     final stats = ref.watch(vpnStatsProvider).valueOrNull;
-    final down = _speed(stats?.downloadSpeed);
-    final up = _speed(stats?.uploadSpeed);
+    final down = formatSpeed(stats?.downloadSpeed);
+    final up = formatSpeed(stats?.uploadSpeed);
     // 延迟来源:连接后优先用内核 urltest 实测(代理真实 RTT);urltest 还没探过时
     // 回退用节点页的 TCP 探针 ping,尽量不显示 —。都没有才 —。
     var livePing = conn.phase == VpnPhase.on ? _bestUrltest(stats) : node.ping;
@@ -202,17 +203,6 @@ class ConnectPage extends ConsumerWidget {
   }
 }
 
-/// 字节/秒 → 动态单位 (数值, 单位):B/s · KB/s · MB/s · GB/s(小数据也看得清)。
-/// null = 未取到,显示 —。
-(String, String) _speed(double? bytesPerSec) {
-  if (bytesPerSec == null) return ('—', 'KB/s');
-  final b = bytesPerSec;
-  if (b < 1024) return (b.toStringAsFixed(0), 'B/s');
-  if (b < 1024 * 1024) return ((b / 1024).toStringAsFixed(1), 'KB/s');
-  if (b < 1024 * 1024 * 1024) return ((b / (1024 * 1024)).toStringAsFixed(1), 'MB/s');
-  return ((b / (1024 * 1024 * 1024)).toStringAsFixed(2), 'GB/s');
-}
-
 /// 内核 urltest 各出站中的最小正延迟(ms);无则 0。
 int _bestUrltest(VpnStatsEvent? s) {
   if (s == null) return 0;

client/lib/util/format.dart

@@ -0,0 +1,21 @@
+// format.dart — 纯数值格式化(支柱 3:纯逻辑与 IO 分离)。
+//
+// 从 widget 抽出的无副作用函数:不碰 BuildContext / 时钟 / 网络,纯输入→输出,
+// 可在 test/unit 里直接断言边界(见 test/unit/format_test.dart)。
+
+/// 字节/秒 → 动态单位 (数值, 单位):B/s · KB/s · MB/s · GB/s(小数据也看得清)。
+/// null = 未取到 → ('—', 'KB/s')。
+(String, String) formatSpeed(double? bytesPerSec) {
+  if (bytesPerSec == null) return ('—', 'KB/s');
+  final b = bytesPerSec;
+  if (b < 1024) return (b.toStringAsFixed(0), 'B/s');
+  if (b < 1024 * 1024) return ((b / 1024).toStringAsFixed(1), 'KB/s');
+  if (b < 1024 * 1024 * 1024) return ((b / (1024 * 1024)).toStringAsFixed(1), 'MB/s');
+  return ((b / (1024 * 1024 * 1024)).toStringAsFixed(2), 'GB/s');
+}
+
+/// 时长 → HH:MM:SS(连接计时;小时不封顶)。
+String formatDuration(Duration d) {
+  String two(int n) => n.toString().padLeft(2, '0');
+  return '${two(d.inHours)}:${two(d.inMinutes % 60)}:${two(d.inSeconds % 60)}';
+}

client/lib/widgets/connect_button.dart

@@ -12,6 +12,7 @@ import 'package:flutter/material.dart';
 
 import '../pangolin_theme.dart';
 import '../state/connection_provider.dart';
+import '../util/format.dart';
 import 'pangolin_icons.dart';
 
 class ConnectButton extends StatefulWidget {
@@ -50,11 +51,6 @@ class _ConnectButtonState extends State<ConnectButton> with SingleTickerProvider
     super.dispose();
   }
 
-  String _fmt(Duration d) {
-    String two(int n) => n.toString().padLeft(2, '0');
-    return '${two(d.inHours)}:${two(d.inMinutes % 60)}:${two(d.inSeconds % 60)}';
-  }
-
   @override
   Widget build(BuildContext context) {
     final c = context.pangolin;
@@ -124,7 +120,7 @@ class _ConnectButtonState extends State<ConnectButton> with SingleTickerProvider
                     Icon(icon, size: 50, color: fg),
                     const SizedBox(height: 6),
                     if (s == VpnPhase.on) ...[
-                      Text(_fmt(widget.elapsed),
+                      Text(formatDuration(widget.elapsed),
                           style: PangolinText.mono
                               .copyWith(color: fg, fontSize: 18, fontWeight: FontWeight.w600)),
                       Text(widget.secureLabel,

client/test/unit/format_test.dart

@@ -0,0 +1,58 @@
+// format_test.dart — L1 数值格式化纯函数单测(支柱 3:纯逻辑、确定性、零依赖)。
+import 'package:flutter_test/flutter_test.dart';
+import 'package:pangolin_vpn/util/format.dart';
+
+void main() {
+  group('formatSpeed(字节/秒 → 数值+单位)', () {
+    test('null → —/KB/s(未取到)', () {
+      expect(formatSpeed(null), ('—', 'KB/s'));
+    });
+
+    test('0 → 0 B/s', () {
+      expect(formatSpeed(0), ('0', 'B/s'));
+    });
+
+    test('< 1KB 用 B/s 且取整', () {
+      expect(formatSpeed(512), ('512', 'B/s'));
+      expect(formatSpeed(1023), ('1023', 'B/s'));
+    });
+
+    test('KB/s 边界(1024)与一位小数', () {
+      expect(formatSpeed(1024), ('1.0', 'KB/s'));
+      expect(formatSpeed(1536), ('1.5', 'KB/s'));
+    });
+
+    test('MB/s 边界(1024^2)', () {
+      expect(formatSpeed(1024 * 1024), ('1.0', 'MB/s'));
+      expect(formatSpeed(1024 * 1024 * 5 + 512 * 1024), ('5.5', 'MB/s'));
+    });
+
+    test('GB/s 边界(1024^3)与两位小数', () {
+      expect(formatSpeed(1024 * 1024 * 1024), ('1.00', 'GB/s'));
+      expect(formatSpeed(2.5 * 1024 * 1024 * 1024), ('2.50', 'GB/s'));
+    });
+  });
+
+  group('formatDuration(时长 → HH:MM:SS)', () {
+    test('0 → 00:00:00', () {
+      expect(formatDuration(Duration.zero), '00:00:00');
+    });
+
+    test('秒/分补零', () {
+      expect(formatDuration(const Duration(seconds: 5)), '00:00:05');
+      expect(formatDuration(const Duration(minutes: 3, seconds: 9)), '00:03:09');
+    });
+
+    test('小时不封顶(对齐连接计时 01:04:59)', () {
+      expect(
+        formatDuration(const Duration(hours: 1, minutes: 4, seconds: 59)),
+        '01:04:59',
+      );
+      expect(formatDuration(const Duration(hours: 100)), '100:00:00');
+    });
+
+    test('分/秒取模 60(不溢出进位错乱)', () {
+      expect(formatDuration(const Duration(minutes: 90)), '01:30:00');
+    });
+  });
+}