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/HealthMonitoringOptionsValidatorTests.cs

@@ -0,0 +1,73 @@
+using Microsoft.Extensions.Options;
+
+namespace ScadaLink.HealthMonitoring.Tests;
+
+/// <summary>
+/// HealthMonitoring-014 regression: <see cref="HealthMonitoringOptions"/> intervals
+/// are fed straight into <c>new PeriodicTimer(...)</c>, which throws
+/// <see cref="ArgumentOutOfRangeException"/> for a zero/negative period. A
+/// misconfigured <c>appsettings.json</c> must be rejected by an
+/// <see cref="IValidateOptions{TOptions}"/> with a clear, key-naming message
+/// rather than crashing the hosted service with an opaque exception.
+/// </summary>
+public class HealthMonitoringOptionsValidatorTests
+{
+    private static ValidateOptionsResult Validate(HealthMonitoringOptions options) =>
+        new HealthMonitoringOptionsValidator().Validate(Options.DefaultName, options);
+
+    [Fact]
+    public void DefaultOptions_AreValid()
+    {
+        var result = Validate(new HealthMonitoringOptions());
+        Assert.True(result.Succeeded, result.FailureMessage);
+    }
+
+    [Fact]
+    public void ZeroReportInterval_IsRejected()
+    {
+        var result = Validate(new HealthMonitoringOptions { ReportInterval = TimeSpan.Zero });
+
+        Assert.True(result.Failed);
+        Assert.Contains("ReportInterval", result.FailureMessage);
+    }
+
+    [Fact]
+    public void NegativeReportInterval_IsRejected()
+    {
+        var result = Validate(new HealthMonitoringOptions { ReportInterval = TimeSpan.FromSeconds(-1) });
+
+        Assert.True(result.Failed);
+        Assert.Contains("ReportInterval", result.FailureMessage);
+    }
+
+    [Fact]
+    public void ZeroOfflineTimeout_IsRejected()
+    {
+        var result = Validate(new HealthMonitoringOptions { OfflineTimeout = TimeSpan.Zero });
+
+        Assert.True(result.Failed);
+        Assert.Contains("OfflineTimeout", result.FailureMessage);
+    }
+
+    [Fact]
+    public void ZeroCentralOfflineTimeout_IsRejected()
+    {
+        var result = Validate(new HealthMonitoringOptions { CentralOfflineTimeout = TimeSpan.Zero });
+
+        Assert.True(result.Failed);
+        Assert.Contains("CentralOfflineTimeout", result.FailureMessage);
+    }
+
+    [Fact]
+    public void CentralOfflineTimeout_ShorterThanOfflineTimeout_IsRejected()
+    {
+        var result = Validate(new HealthMonitoringOptions
+        {
+            OfflineTimeout = TimeSpan.FromSeconds(60),
+            CentralOfflineTimeout = TimeSpan.FromSeconds(30)
+        });
+
+        Assert.True(result.Failed);
+        Assert.Contains("CentralOfflineTimeout", result.FailureMessage);
+    }
+}