backend: confirm a registered update by itself after a delay when auto update is switched on [CI]

backend/tests/MoShiro.Backend.Tests/BackendUpdateTests.cs

@@ -69,6 +69,33 @@ public sealed class BackendUpdateTests : IAsyncLifetime
         Assert.Equal(HttpStatusCode.Conflict, replay.StatusCode);
     }
 
+    /// <summary>自动更新默认关；打开之后只在新版本登记满设定的时间才确认，走的是和手动一样的路径（先备份）。</summary>
+    [Fact]
+    public async Task AutoUpdate_IsOffByDefault_AndConfirmsOnlyAfterTheOfferHasAged()
+    {
+        BackendOptions options = _backend.Services.GetRequiredService<BackendOptions>();
+        var updater = _backend.Services.GetRequiredService<BackendAutoUpdater>();
+        using HttpResponseMessage old = await PublishAsync(10); // seq 是发布时间（秒）：1970 年，早就过了等待时间
+        Assert.Equal(HttpStatusCode.Created, old.StatusCode);
+
+        Assert.False(await updater.RunOnceAsync(default)); // 默认关
+        Assert.Equal(0, _backend.Restarts.Count);
+
+        options.AutoUpdate = true;
+        options.AutoUpdateDelayMinutes = 10;
+        using HttpResponseMessage fresh = await PublishAsync(TimeProvider.System.GetUtcNow().ToUnixTimeSeconds());
+        Assert.Equal(HttpStatusCode.Created, fresh.StatusCode);
+        Assert.False(await updater.RunOnceAsync(default)); // 刚登记的版本还要等
+        Assert.Equal(0, _backend.Restarts.Count);
+
+        options.AutoUpdateDelayMinutes = 0;
+        Assert.True(await updater.RunOnceAsync(default));
+        Assert.Equal(1, _backend.Restarts.Count);
+        Assert.Single(Directory.GetFiles(Path.Combine(_backend.DataDirectory, "backups"), "pre-update-*.db")); // 先备份
+        Assert.False(await updater.RunOnceAsync(default)); // 已经在更新，不会再确认第二次
+        Assert.Equal(1, _backend.Restarts.Count);
+    }
+
     [Fact]
     public async Task Confirm_BacksUpTheDatabase_ThenExits_AndRejectsASupersededSequence()
     {