fix(central-ui): resolve CentralUI-015..019 — pager windowing, logout CSRF, narrowed catch blocks, coverage; CentralUI-015 re-triaged Won't Fix

tests/ScadaLink.CentralUI.Tests/Shared/DataTablePagerTests.cs

@@ -0,0 +1,68 @@
+using Bunit;
+using Microsoft.AspNetCore.Components;
+using ScadaLink.CentralUI.Components.Shared;
+
+namespace ScadaLink.CentralUI.Tests.Shared;
+
+/// <summary>
+/// Regression tests for CentralUI-016. <c>DataTable</c> looped
+/// <c>for i = 1..totalPages</c> and emitted one numbered <c>&lt;li&gt;</c>
+/// button per page; a few thousand records at page size 25 rendered hundreds
+/// of buttons into the diff on every state change. The fix windows the pager
+/// so only first / last / a small range around the current page render.
+/// </summary>
+public class DataTablePagerTests : BunitContext
+{
+    private IRenderedComponent<DataTable<int>> RenderTable(int itemCount, int pageSize = 25)
+    {
+        return Render<DataTable<int>>(parameters => parameters
+            .Add(p => p.Items, Enumerable.Range(1, itemCount).ToList())
+            .Add(p => p.PageSize, pageSize)
+            .Add(p => p.ShowSearch, false)
+            .Add(p => p.HeaderContent, (RenderFragment)(b => b.AddMarkupContent(0, "<th>N</th>")))
+            .Add(p => p.RowContent, (RenderFragment<int>)(item => b => b.AddMarkupContent(0, $"<tr><td>{item}</td></tr>"))));
+    }
+
+    private static int NumberedPageButtons(IRenderedComponent<DataTable<int>> cut)
+        => cut.FindAll("ul.pagination li.page-item button")
+              .Count(b => int.TryParse(b.TextContent.Trim(), out _));
+
+    [Fact]
+    public void Pager_WithThousandsOfPages_RendersWindowedNotEveryPage()
+    {
+        // 5000 items / 25 = 200 pages. The pre-fix pager rendered 200 numbered
+        // buttons; the windowed pager renders at most a dozen.
+        var cut = RenderTable(itemCount: 5000);
+
+        var numbered = NumberedPageButtons(cut);
+
+        Assert.True(numbered <= 12,
+            $"Expected a windowed pager (<= 12 numbered buttons) but rendered {numbered}.");
+    }
+
+    [Fact]
+    public void Pager_SmallDataset_StillRendersEveryPage()
+    {
+        // 5 pages — small enough to render all numbered buttons (no windowing harm).
+        var cut = RenderTable(itemCount: 125);
+
+        var numbered = NumberedPageButtons(cut);
+
+        Assert.Equal(5, numbered);
+    }
+
+    [Fact]
+    public void Pager_WindowedAroundCurrentPage_AlwaysIncludesFirstAndLast()
+    {
+        var cut = RenderTable(itemCount: 5000); // 200 pages
+
+        var numbered = cut.FindAll("ul.pagination li.page-item button")
+            .Select(b => b.TextContent.Trim())
+            .Where(t => int.TryParse(t, out _))
+            .ToList();
+
+        // First and last page are always reachable from the windowed pager.
+        Assert.Contains("1", numbered);
+        Assert.Contains("200", numbered);
+    }
+}