fix(notification-service): resolve NotificationService-010,011,012 — disconnect SMTP on failure, relocate exception type, OAuth2/token-cache test coverage

tests/ScadaLink.NotificationService.Tests/NotificationDeliveryServiceTests.cs

@@ -1,3 +1,4 @@
+using System.Text.Json;
 using MailKit;
 using MailKit.Net.Smtp;
 using Microsoft.Extensions.Logging.Abstractions;
@@ -407,6 +408,78 @@ public class NotificationDeliveryServiceTests
             storage, new StoreAndForwardOptions(), NullLogger<StoreAndForwardService>.Instance);
     }
 
+    // ── NotificationService-010: SMTP client is disconnected on the failure path ──
+
+    /// <summary>
+    /// An SMTP wrapper that records whether <see cref="DisconnectAsync"/> ran and
+    /// can be told to fail at a chosen stage of the delivery sequence.
+    /// </summary>
+    private sealed class DisconnectTrackingClient : ISmtpClientWrapper, IDisposable
+    {
+        private readonly Func<Exception>? _failOnSend;
+        private readonly Func<Exception>? _failOnAuthenticate;
+
+        public DisconnectTrackingClient(
+            Func<Exception>? failOnSend = null, Func<Exception>? failOnAuthenticate = null)
+        {
+            _failOnSend = failOnSend;
+            _failOnAuthenticate = failOnAuthenticate;
+        }
+
+        public bool Disconnected { get; private set; }
+        public bool Disposed { get; private set; }
+
+        public Task ConnectAsync(string host, int port, SmtpTlsMode tlsMode, int connectionTimeoutSeconds, CancellationToken cancellationToken = default)
+            => Task.CompletedTask;
+
+        public Task AuthenticateAsync(string authType, string? credentials, CancellationToken cancellationToken = default)
+            => _failOnAuthenticate != null ? Task.FromException(_failOnAuthenticate()) : Task.CompletedTask;
+
+        public Task SendAsync(string from, IEnumerable<string> bccRecipients, string subject, string body, CancellationToken cancellationToken = default)
+            => _failOnSend != null ? Task.FromException(_failOnSend()) : Task.CompletedTask;
+
+        public Task DisconnectAsync(CancellationToken cancellationToken = default)
+        {
+            Disconnected = true;
+            return Task.CompletedTask;
+        }
+
+        public void Dispose() => Disposed = true;
+    }
+
+    [Fact]
+    public async Task Send_TransientFailureDuringSend_StillDisconnectsClient()
+    {
+        // NS-010: DisconnectAsync used to run only on the success path inside the
+        // try block. A failure in SendAsync left the authenticated connection open
+        // (the SMTP QUIT was never issued), leaking server connection slots under
+        // sustained transient failures.
+        SetupHappyPath();
+        var tracking = new DisconnectTrackingClient(
+            failOnSend: () => new SmtpProtocolException("protocol error"));
+        var service = new NotificationDeliveryService(
+            _repository, () => tracking, NullLogger<NotificationDeliveryService>.Instance);
+
+        await service.SendAsync("ops-team", "Alert", "Body");
+
+        Assert.True(tracking.Disconnected, "DeliverAsync must disconnect the SMTP client even when the send fails");
+    }
+
+    [Fact]
+    public async Task Send_FailureDuringAuthenticate_StillDisconnectsClient()
+    {
+        // NS-010: an AuthenticateAsync failure must also tear the connection down.
+        SetupHappyPath();
+        var tracking = new DisconnectTrackingClient(
+            failOnAuthenticate: () => new SmtpProtocolException("auth handshake failed"));
+        var service = new NotificationDeliveryService(
+            _repository, () => tracking, NullLogger<NotificationDeliveryService>.Instance);
+
+        await service.SendAsync("ops-team", "Alert", "Body");
+
+        Assert.True(tracking.Disconnected, "DeliverAsync must disconnect the SMTP client even when authentication fails");
+    }
+
     // ── NotificationService-005: explicit TLS mode passed through to the wrapper ──
 
     /// <summary>An SMTP wrapper that records the TLS mode and timeout it was connected with.</summary>
@@ -642,4 +715,77 @@ public class NotificationDeliveryServiceTests
         Assert.False(result.Success);
         Assert.Contains("address", result.ErrorMessage, StringComparison.OrdinalIgnoreCase);
     }
+
+    // ── NotificationService-012: OAuth2 delivery path coverage ──
+
+    /// <summary>An SMTP wrapper that records the auth type and credentials it received.</summary>
+    private sealed class RecordingAuthClient : ISmtpClientWrapper
+    {
+        public string? AuthType { get; private set; }
+        public string? Credentials { get; private set; }
+        public Task ConnectAsync(string host, int port, SmtpTlsMode tlsMode, int connectionTimeoutSeconds, CancellationToken cancellationToken = default)
+            => Task.CompletedTask;
+        public Task AuthenticateAsync(string authType, string? credentials, CancellationToken cancellationToken = default)
+        {
+            AuthType = authType;
+            Credentials = credentials;
+            return Task.CompletedTask;
+        }
+        public Task SendAsync(string from, IEnumerable<string> bccRecipients, string subject, string body, CancellationToken cancellationToken = default)
+            => Task.CompletedTask;
+        public Task DisconnectAsync(CancellationToken cancellationToken = default) => Task.CompletedTask;
+    }
+
+    private static OAuth2TokenService CreateTokenService(string accessToken, int expiresIn = 3600)
+    {
+        var json = JsonSerializer.Serialize(new
+        {
+            access_token = accessToken,
+            expires_in = expiresIn,
+            token_type = "Bearer"
+        });
+        var factory = Substitute.For<IHttpClientFactory>();
+        factory.CreateClient(Arg.Any<string>())
+            .Returns(_ => new HttpClient(new StubHttpHandler(json)));
+        return new OAuth2TokenService(factory, NullLogger<OAuth2TokenService>.Instance);
+    }
+
+    private sealed class StubHttpHandler : HttpMessageHandler
+    {
+        private readonly string _json;
+        public StubHttpHandler(string json) => _json = json;
+        protected override Task<HttpResponseMessage> SendAsync(
+            HttpRequestMessage request, CancellationToken cancellationToken)
+            => Task.FromResult(new HttpResponseMessage(System.Net.HttpStatusCode.OK)
+            {
+                Content = new StringContent(_json)
+            });
+    }
+
+    [Fact]
+    public async Task Send_OAuth2Config_AuthenticatesWithResolvedAccessToken()
+    {
+        // NS-012: the OAuth2 delivery branch in DeliverAsync (token resolution during
+        // a send) was never exercised — every other test uses Basic Auth and a null
+        // token service. The credentials reaching the SMTP client must be the access
+        // token from OAuth2TokenService, not the raw tenant:client:secret triple.
+        var cfg = new SmtpConfiguration("smtp.office365.com", "oauth2", "noreply@example.com")
+        {
+            Id = 1, Port = 587, Credentials = "tenant1:client1:secret1", TlsMode = "starttls"
+        };
+        SetupHappyPathWithSmtp(cfg);
+
+        var recording = new RecordingAuthClient();
+        var service = new NotificationDeliveryService(
+            _repository,
+            () => recording,
+            NullLogger<NotificationDeliveryService>.Instance,
+            tokenService: CreateTokenService("oauth2-access-token-xyz"));
+
+        var result = await service.SendAsync("ops-team", "Alert", "Body");
+
+        Assert.True(result.Success);
+        Assert.Equal("oauth2", recording.AuthType);
+        Assert.Equal("oauth2-access-token-xyz", recording.Credentials);
+    }
 }

tests/ScadaLink.NotificationService.Tests/OAuth2TokenServiceTests.cs

@@ -124,6 +124,105 @@ public class OAuth2TokenServiceTests
         Assert.Equal(2, handler.CallCount); // one per distinct credential, not per call
     }
 
+    // ── NotificationService-012: token expiry/refresh and concurrent acquisition ──
+
+    [Fact]
+    public async Task GetTokenAsync_ExpiredToken_RefreshesOnNextCall()
+    {
+        // NS-012: token expiry/refresh was untested — the cache test used a 3600s
+        // token so the refresh branch never ran. The service refreshes 60s before
+        // the stated expiry, so an expires_in of 60 makes the token immediately
+        // stale and the next call must fetch a fresh one.
+        var handler = new SequenceHttpMessageHandler(
+            TokenJson("first-token", expiresIn: 60),
+            TokenJson("second-token", expiresIn: 3600));
+        var client = new HttpClient(handler);
+        var factory = CreateMockFactory(client);
+        var service = new OAuth2TokenService(factory, NullLogger<OAuth2TokenService>.Instance);
+
+        var token1 = await service.GetTokenAsync("tenant:client:secret");
+        var token2 = await service.GetTokenAsync("tenant:client:secret");
+
+        Assert.Equal("first-token", token1);
+        Assert.Equal("second-token", token2); // refreshed because the first was already stale
+        Assert.Equal(2, handler.CallCount);
+    }
+
+    [Fact]
+    public async Task GetTokenAsync_ConcurrentCalls_MakeExactlyOneHttpRequest()
+    {
+        // NS-012: the double-checked-locking path was never exercised. Many callers
+        // racing for the same uncached credential must collapse to a single token
+        // fetch, not one HTTP call per caller.
+        var handler = new SlowCountingHttpMessageHandler(
+            TokenJson("concurrent-token", expiresIn: 3600), delay: TimeSpan.FromMilliseconds(100));
+        var client = new HttpClient(handler);
+        var factory = CreateMockFactory(client);
+        var service = new OAuth2TokenService(factory, NullLogger<OAuth2TokenService>.Instance);
+
+        var tasks = Enumerable.Range(0, 20)
+            .Select(_ => service.GetTokenAsync("tenant:client:secret"))
+            .ToArray();
+        var tokens = await Task.WhenAll(tasks);
+
+        Assert.All(tokens, t => Assert.Equal("concurrent-token", t));
+        Assert.Equal(1, handler.CallCount);
+    }
+
+    private static string TokenJson(string accessToken, int expiresIn) =>
+        JsonSerializer.Serialize(new
+        {
+            access_token = accessToken,
+            expires_in = expiresIn,
+            token_type = "Bearer"
+        });
+
+    /// <summary>HTTP handler returning a different response per invocation, in order.</summary>
+    private class SequenceHttpMessageHandler : HttpMessageHandler
+    {
+        private readonly string[] _responses;
+        public int CallCount { get; private set; }
+
+        public SequenceHttpMessageHandler(params string[] responses) => _responses = responses;
+
+        protected override Task<HttpResponseMessage> SendAsync(
+            HttpRequestMessage request, CancellationToken cancellationToken)
+        {
+            var body = _responses[Math.Min(CallCount, _responses.Length - 1)];
+            CallCount++;
+            return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = new StringContent(body)
+            });
+        }
+    }
+
+    /// <summary>HTTP handler that delays and counts invocations (thread-safe count).</summary>
+    private class SlowCountingHttpMessageHandler : HttpMessageHandler
+    {
+        private readonly string _response;
+        private readonly TimeSpan _delay;
+        private int _callCount;
+        public int CallCount => _callCount;
+
+        public SlowCountingHttpMessageHandler(string response, TimeSpan delay)
+        {
+            _response = response;
+            _delay = delay;
+        }
+
+        protected override async Task<HttpResponseMessage> SendAsync(
+            HttpRequestMessage request, CancellationToken cancellationToken)
+        {
+            Interlocked.Increment(ref _callCount);
+            await Task.Delay(_delay, cancellationToken);
+            return new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = new StringContent(_response)
+            };
+        }
+    }
+
     /// <summary>
     /// HTTP handler that returns a distinct access token per tenant id, parsed from
     /// the request URL (<c>https://login.microsoftonline.com/{tenantId}/...</c>).