feat(stability): unify readiness and recovery

backend-tests/HealthControllerTests.cs

@@ -0,0 +1,69 @@
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using Nexus.Api.Controllers;
+using Xunit;
+
+namespace Nexus.Api.Tests;
+
+public sealed class HealthControllerTests
+{
+    [Fact]
+    public async Task Ready_Returns200_WhenRequiredChecksAreHealthy()
+    {
+        using var provider = BuildProvider(HealthCheckResult.Healthy());
+        var controller = new HealthController(
+            runtime: null!,
+            provider.GetRequiredService<HealthCheckService>());
+
+        var result = await controller.Ready(CancellationToken.None);
+
+        Assert.Equal(StatusCodes.Status200OK, Assert.IsAssignableFrom<IStatusCodeHttpResult>(result).StatusCode);
+    }
+
+    [Fact]
+    public async Task Ready_Returns503_WhenRequiredCheckIsUnhealthy()
+    {
+        using var provider = BuildProvider(HealthCheckResult.Unhealthy("database unavailable"));
+        var controller = new HealthController(
+            runtime: null!,
+            provider.GetRequiredService<HealthCheckService>());
+
+        var result = await controller.Ready(CancellationToken.None);
+
+        Assert.Equal(
+            StatusCodes.Status503ServiceUnavailable,
+            Assert.IsAssignableFrom<IStatusCodeHttpResult>(result).StatusCode);
+    }
+
+    [Fact]
+    public async Task Ready_Returns503_WhenPostgreSqlCannotBeReached()
+    {
+        var services = new ServiceCollection();
+        services.AddLogging();
+        services.AddHealthChecks()
+            .AddNpgSql(
+                "Host=127.0.0.1;Port=1;Database=nexus;Username=nexus;Password=unused;Timeout=1;Command Timeout=1",
+                name: "postgresql",
+                tags: ["database", "ready"]);
+        using var provider = services.BuildServiceProvider();
+        var controller = new HealthController(
+            runtime: null!,
+            provider.GetRequiredService<HealthCheckService>());
+
+        var result = await controller.Ready(CancellationToken.None);
+
+        Assert.Equal(
+            StatusCodes.Status503ServiceUnavailable,
+            Assert.IsAssignableFrom<IStatusCodeHttpResult>(result).StatusCode);
+    }
+
+    private static ServiceProvider BuildProvider(HealthCheckResult result)
+    {
+        var services = new ServiceCollection();
+        services.AddLogging();
+        services.AddHealthChecks()
+            .AddCheck("required", () => result, tags: ["ready"]);
+        return services.BuildServiceProvider();
+    }
+}