Initial curated itworx-knowledge-hub source from 3b1751d0d9dee551aa6994eee0093704dc334817

tests/backend/ItWorx.KnowledgeHub.IntegrationTests/Auth/ConcurrentLoginTests.cs

@@ -0,0 +1,29 @@
+using System.Net;
+using ItWorx.KnowledgeHub.IntegrationTests.Infrastructure;
+
+namespace ItWorx.KnowledgeHub.IntegrationTests.Auth;
+
+/// <summary>Regression coverage for a real bug found via E2E testing: two concurrent
+/// logins for the same account raced on ASP.NET Core Identity's optimistic-concurrency
+/// token while recording the last-login timestamp, turning a successful authentication
+/// into a 500 for whichever request lost the race.</summary>
+[Collection(PostgresTestGroup.Name)]
+public sealed class ConcurrentLoginTests(PostgresContainerFixture postgres) : OwnerSetupTestBase(postgres)
+{
+    [Fact]
+    public async Task Concurrent_logins_for_the_same_account_never_fail_with_a_server_error()
+    {
+        using var clientA = Factory.CreateClient();
+        using var clientB = Factory.CreateClient();
+
+        var loginA = SetupHelper.LoginAsync(clientA, OwnerEmail, OwnerPassword);
+        var loginB = SetupHelper.LoginAsync(clientB, OwnerEmail, OwnerPassword);
+
+        var results = await Task.WhenAll(loginA, loginB);
+
+        foreach (var response in results)
+        {
+            Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        }
+    }
+}