too much for one commit

tests/EntKube.Clusters.Tests/Features/DiscoverPrometheusHandlerTests.cs

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+using EntKube.Clusters.Domain;
+using EntKube.Clusters.Features.DiscoverPrometheus;
+using EntKube.Clusters.Infrastructure;
+using EntKube.SharedKernel.Domain;
+using FluentAssertions;
+
+namespace EntKube.Clusters.Tests.Features;
+
+public class DiscoverPrometheusHandlerTests
+{
+    private readonly InMemoryClusterRepository repository;
+
+    public DiscoverPrometheusHandlerTests()
+    {
+        repository = new InMemoryClusterRepository();
+    }
+
+    [Fact]
+    public async Task HandleAsync_WithDiscoveredEndpoints_StoresThemOnCluster()
+    {
+        // Arrange — A registered cluster and a scanner that finds two Prometheus instances.
+
+        KubernetesCluster cluster = KubernetesCluster.Register(
+            "production",
+            "https://k8s.example.com:6443",
+            "kubeconfig-data",
+            Guid.NewGuid(),
+            "prod-ctx", Guid.NewGuid());
+
+        await repository.AddAsync(cluster);
+
+        List<PrometheusEndpoint> fakeEndpoints = new()
+        {
+            new PrometheusEndpoint("http://prometheus.monitoring:9090", "monitoring", "prometheus-server"),
+            new PrometheusEndpoint("http://prometheus.observability:9090", "observability", "prom-stack")
+        };
+
+        FakePrometheusScanner scanner = new(fakeEndpoints);
+        DiscoverPrometheusHandler handler = new(repository, scanner);
+
+        // Act — Run discovery on the cluster.
+
+        Result<List<PrometheusEndpoint>> result = await handler.HandleAsync(cluster.Id);
+
+        // Assert — Both endpoints should be stored and returned.
+
+        result.IsSuccess.Should().BeTrue();
+        result.Value.Should().HaveCount(2);
+        result.Value![0].Namespace.Should().Be("monitoring");
+        result.Value[1].Namespace.Should().Be("observability");
+
+        KubernetesCluster? updated = await repository.GetByIdAsync(cluster.Id);
+        updated!.PrometheusEndpoints.Should().HaveCount(2);
+    }
+
+    [Fact]
+    public async Task HandleAsync_WithNoPrometheus_ReturnsEmptyList()
+    {
+        // Arrange — A cluster with no Prometheus running.
+
+        KubernetesCluster cluster = KubernetesCluster.Register(
+            "staging",
+            "https://staging.example.com:6443",
+            "kubeconfig-data",
+            Guid.NewGuid(),
+            "staging-ctx", Guid.NewGuid());
+
+        await repository.AddAsync(cluster);
+
+        FakePrometheusScanner scanner = new(new List<PrometheusEndpoint>());
+        DiscoverPrometheusHandler handler = new(repository, scanner);
+
+        // Act
+
+        Result<List<PrometheusEndpoint>> result = await handler.HandleAsync(cluster.Id);
+
+        // Assert — Success but empty list. No Prometheus found is not an error.
+
+        result.IsSuccess.Should().BeTrue();
+        result.Value.Should().BeEmpty();
+    }
+
+    [Fact]
+    public async Task HandleAsync_WithNonExistentCluster_ReturnsFailure()
+    {
+        // Arrange
+
+        FakePrometheusScanner scanner = new(new List<PrometheusEndpoint>());
+        DiscoverPrometheusHandler handler = new(repository, scanner);
+
+        // Act
+
+        Result<List<PrometheusEndpoint>> result = await handler.HandleAsync(Guid.NewGuid());
+
+        // Assert
+
+        result.IsFailure.Should().BeTrue();
+        result.Error.Should().Contain("not found");
+    }
+
+    [Fact]
+    public async Task HandleAsync_ReplacesExistingEndpoints_OnRediscovery()
+    {
+        // Arrange — A cluster that already had endpoints from a previous scan.
+
+        KubernetesCluster cluster = KubernetesCluster.Register(
+            "production",
+            "https://k8s.example.com:6443",
+            "kubeconfig-data",
+            Guid.NewGuid(),
+            "prod-ctx", Guid.NewGuid());
+
+        cluster.SetPrometheusEndpoints(new List<PrometheusEndpoint>
+        {
+            new("http://old-prometheus:9090", "legacy", "old-prom")
+        });
+
+        await repository.AddAsync(cluster);
+
+        // A new scan finds a different Prometheus.
+
+        List<PrometheusEndpoint> newEndpoints = new()
+        {
+            new PrometheusEndpoint("http://prometheus.monitoring:9090", "monitoring", "prometheus-server")
+        };
+
+        FakePrometheusScanner scanner = new(newEndpoints);
+        DiscoverPrometheusHandler handler = new(repository, scanner);
+
+        // Act
+
+        Result<List<PrometheusEndpoint>> result = await handler.HandleAsync(cluster.Id);
+
+        // Assert — The old endpoint is replaced by the new one.
+
+        result.IsSuccess.Should().BeTrue();
+        result.Value.Should().HaveCount(1);
+        result.Value![0].ServiceName.Should().Be("prometheus-server");
+
+        KubernetesCluster? updated = await repository.GetByIdAsync(cluster.Id);
+        updated!.PrometheusEndpoints.Should().HaveCount(1);
+    }
+}
+
+/// <summary>
+/// Test double that returns pre-configured Prometheus endpoints
+/// without actually connecting to a Kubernetes cluster.
+/// </summary>
+public class FakePrometheusScanner : IPrometheusScanner
+{
+    private readonly List<PrometheusEndpoint> endpoints;
+
+    public FakePrometheusScanner(List<PrometheusEndpoint> endpoints)
+    {
+        this.endpoints = endpoints;
+    }
+
+    public Task<List<PrometheusEndpoint>> ScanAsync(KubernetesCluster cluster, CancellationToken ct = default)
+    {
+        return Task.FromResult(endpoints);
+    }
+}