refactor(kpi): K13/K15 trend review fixups — per-metric isolation, disable-during-load + logging, loading-flag finally, test coverage

tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Pages/HealthPageTests.cs

@@ -237,10 +237,13 @@ public class HealthPageTests : BunitContext
             Assert.Contains("data-test=\"site-health-trends\"", cut.Markup);
             Assert.Contains("data-test=\"site-health-trends-site\"", cut.Markup);
             // The four metric charts render (the shared KpiTrendChart slug hook),
-            // and the seeded non-empty series draws a polyline.
+            // and the seeded non-empty series draws a polyline. The "S&F Buffer
+            // Depth" title slugifies to "s-f-buffer-depth" (the & and the spaces
+            // each collapse to a dash) — see KpiTrendChart.Slugify.
             Assert.Contains("kpi-trend-connections-down", cut.Markup);
             Assert.Contains("kpi-trend-dead-letters", cut.Markup);
             Assert.Contains("kpi-trend-script-errors", cut.Markup);
+            Assert.Contains("kpi-trend-s-f-buffer-depth", cut.Markup);
             Assert.Contains("<polyline", cut.Markup);
         });
     }

tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Pages/NotificationKpisPageTests.cs

@@ -178,6 +178,44 @@ public class NotificationKpisPageTests : BunitContext
         });
     }
 
+    [Fact]
+    public void PartialTrendFailure_IsolatesToTheFailingMetric()
+    {
+        // Per-metric isolation (K13 fixup): the substitute returns a known series
+        // for two metrics but THROWS for "parkedCount". The two surviving charts
+        // must still draw their polylines while only the failing chart degrades to
+        // the unavailable placeholder — one metric's failure no longer blanks all
+        // three (and does not discard the already-fetched siblings).
+        _kpiHistory.GetSeriesAsync(
+                Arg.Any<string>(), Arg.Is<string>(m => m == "parkedCount"), Arg.Any<string>(),
+                Arg.Any<string?>(), Arg.Any<DateTime>(), Arg.Any<DateTime>(),
+                Arg.Any<int?>(), Arg.Any<CancellationToken>())
+            .Returns<Task<IReadOnlyList<KpiSeriesPoint>>>(_ => throw new InvalidOperationException("parked metric down"));
+
+        var cut = Render<NotificationKpisPage>();
+
+        cut.WaitForAssertion(() =>
+        {
+            // The page is still alive — KPI tiles render and the trends section
+            // never went fully blank.
+            Assert.Contains("Queue Depth", cut.Markup);
+            Assert.NotNull(cut.Find("[data-test=\"notification-trends\"]"));
+
+            // The two surviving metrics (queueDepth, deliveredLastInterval) drew
+            // their polylines …
+            var queueChart = cut.Find("[data-test=\"kpi-trend-queue-depth\"]");
+            Assert.Contains("<polyline", queueChart.InnerHtml);
+            var deliveredChart = cut.Find("[data-test=\"kpi-trend-delivered-interval\"]");
+            Assert.Contains("<polyline", deliveredChart.InnerHtml);
+
+            // … while only the failing "Parked" chart degraded to the unavailable
+            // placeholder (no polyline, the short error message instead).
+            var parkedChart = cut.Find("[data-test=\"kpi-trend-parked\"]");
+            Assert.DoesNotContain("<polyline", parkedChart.InnerHtml);
+            Assert.Contains("Trend data unavailable.", parkedChart.InnerHtml);
+        });
+    }
+
     [Fact]
     public void TrendQueryFailure_DoesNotBreakPage()
     {