fix(health-monitoring): resolve HealthMonitoring-013,014,016 — shorter-timeout cadence, options validation, injected TimeProvider; HealthMonitoring-015 left open (cross-module design decision)

tests/ScadaLink.HealthMonitoring.Tests/SiteHealthCollectorTests.cs

@@ -131,6 +131,24 @@ public class SiteHealthCollectorTests
         Assert.InRange(report.ReportTimestamp, before, after);
     }
 
+    /// <summary>
+    /// HealthMonitoring-016 regression: <see cref="SiteHealthCollector.CollectReport"/>
+    /// must stamp <c>ReportTimestamp</c> from an injected <see cref="TimeProvider"/>
+    /// (consistent with the rest of the module), not directly from
+    /// <c>DateTimeOffset.UtcNow</c>, so the report timestamp is deterministically
+    /// testable against a known instant.
+    /// </summary>
+    [Fact]
+    public void CollectReport_StampsTimestamp_FromInjectedTimeProvider()
+    {
+        var fixedInstant = new DateTimeOffset(2026, 5, 17, 9, 30, 0, TimeSpan.Zero);
+        var collector = new SiteHealthCollector(new TestTimeProvider(fixedInstant));
+
+        var report = collector.CollectReport("site-1");
+
+        Assert.Equal(fixedInstant, report.ReportTimestamp);
+    }
+
     [Fact]
     public void CollectReport_SequenceNumberIsZero_CallerAssignsIt()
     {