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/PagerWindowTests.cs

@@ -0,0 +1,67 @@
+using ScadaLink.CentralUI.Components.Shared;
+
+namespace ScadaLink.CentralUI.Tests.Shared;
+
+/// <summary>
+/// Unit tests for the <see cref="PagerWindow"/> helper introduced for
+/// CentralUI-016 — windowed pagination that keeps the rendered button count
+/// bounded regardless of total page count.
+/// </summary>
+public class PagerWindowTests
+{
+    [Fact]
+    public void Build_SmallPageCount_ReturnsEveryPage_NoEllipsis()
+    {
+        var pages = PagerWindow.Build(currentPage: 3, totalPages: 5);
+
+        Assert.Equal(new[] { 1, 2, 3, 4, 5 }, pages);
+    }
+
+    [Fact]
+    public void Build_LargePageCount_IsBounded_AndIncludesFirstAndLast()
+    {
+        var pages = PagerWindow.Build(currentPage: 100, totalPages: 200);
+
+        Assert.Contains(1, pages);
+        Assert.Contains(200, pages);
+        Assert.Contains(100, pages);
+        // First, ellipsis, window of 5, ellipsis, last — never the full 200.
+        Assert.True(pages.Count <= 12, $"Expected a bounded window but got {pages.Count} entries.");
+    }
+
+    [Fact]
+    public void Build_LargePageCount_InsertsEllipsisForGaps()
+    {
+        // 0 is the ellipsis sentinel.
+        var pages = PagerWindow.Build(currentPage: 100, totalPages: 200);
+
+        Assert.Contains(0, pages);
+    }
+
+    [Fact]
+    public void Build_CurrentNearStart_NoLeadingEllipsis()
+    {
+        var pages = PagerWindow.Build(currentPage: 1, totalPages: 200);
+
+        // Pages 1..3 are contiguous from the start, so no ellipsis before them.
+        Assert.Equal(1, pages[0]);
+        Assert.NotEqual(0, pages[1]);
+    }
+
+    [Fact]
+    public void Build_ClampsOutOfRangeCurrentPage()
+    {
+        var pages = PagerWindow.Build(currentPage: 999, totalPages: 200);
+
+        Assert.Contains(200, pages);
+        Assert.True(pages.Count <= 12);
+    }
+
+    [Theory]
+    [InlineData(0)]
+    [InlineData(-3)]
+    public void Build_NonPositiveTotalPages_ReturnsEmpty(int totalPages)
+    {
+        Assert.Empty(PagerWindow.Build(currentPage: 1, totalPages: totalPages));
+    }
+}