Add unit tests for IdleFetchAsync

Author: daniel-lerch

server/Mailist.Tests/ImapClientTests.cs

@@ -0,0 +1,92 @@
+using Mailist.Utilities;
+using MailKit;
+using MailKit.Net.Imap;
+using Moq;
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Mailist.Tests;
+
+public class ImapClientTests
+{
+    [Fact]
+    public async Task IdleFetch_ReturnsExistingMessages()
+    {
+        var cancel = new CancellationTokenSource();
+        var client = new Mock<IImapClient>();
+        var folder = new Mock<IMailFolder>();
+        var existingMessage = new Mock<IMessageSummary>();
+        client.Setup(c => c.Capabilities).Returns(ImapCapabilities.Idle);
+        client.Setup(c => c.IdleAsync(It.IsAny<CancellationToken>(), It.IsAny<CancellationToken>()))
+            .Returns(async (CancellationToken doneToken, CancellationToken cancellationToken) =>
+            {
+                try
+                {
+                    using var cts = CancellationTokenSource.CreateLinkedTokenSource(doneToken, cancellationToken);
+                    await Task.Delay(-1, cts.Token);
+                }
+                catch (OperationCanceledException) when (doneToken.IsCancellationRequested)
+                {
+                }
+            });
+        folder.Setup(f => f.IsOpen).Returns(true);
+        folder.Setup(f => f.Count).Returns(1);
+        folder.Setup(f => f.FetchAsync(It.IsAny<int>(), It.IsAny<int>(), It.IsAny<IFetchRequest>(), It.IsAny<CancellationToken>()).Result)
+            .Returns([existingMessage.Object]);
+        existingMessage.Setup(m => m.UniqueId).Returns(new UniqueId(1));
+
+        IAsyncEnumerator<IMessageSummary> enumerator = client.Object
+            .IdleFetchAsync(folder.Object, MessageSummaryItems.UniqueId, cancel.Token)
+            .GetAsyncEnumerator(CancellationToken.None);
+
+        Assert.True(await enumerator.MoveNextAsync());
+        Assert.Same(existingMessage.Object, enumerator.Current);
+
+        cancel.CancelAfter(100);
+        await Assert.ThrowsAnyAsync<OperationCanceledException>(() => enumerator.MoveNextAsync().AsTask());
+    }
+
+    [Fact]
+    public async Task IdleFetch_ReturnsNewlyArrivedMessages()
+    {
+        var cancel = new CancellationTokenSource();
+        var client = new Mock<IImapClient>();
+        var folder = new Mock<IMailFolder>();
+        var newMessage = new Mock<IMessageSummary>();
+        client.Setup(c => c.Capabilities).Returns(ImapCapabilities.Idle);
+        client.Setup(c => c.IdleAsync(It.IsAny<CancellationToken>(), It.IsAny<CancellationToken>()))
+            .Returns(async (CancellationToken doneToken, CancellationToken cancellationToken) =>
+            {
+                try
+                {
+                    using var cts = CancellationTokenSource.CreateLinkedTokenSource(doneToken, cancellationToken);
+                    await Task.Delay(-1, cts.Token);
+                }
+                catch (OperationCanceledException) when (doneToken.IsCancellationRequested)
+                {
+                }
+            });
+        folder.Setup(f => f.IsOpen).Returns(true);
+        folder.Setup(f => f.Count).Returns(0);
+
+        IAsyncEnumerator<IMessageSummary> enumerator = client.Object
+            .IdleFetchAsync(folder.Object, MessageSummaryItems.UniqueId, cancel.Token)
+            .GetAsyncEnumerator(CancellationToken.None);
+
+        ValueTask<bool> task = enumerator.MoveNextAsync();
+        await Task.Delay(100, TestContext.Current.CancellationToken);
+        folder.Setup(f => f.FetchAsync(It.IsAny<int>(), It.IsAny<int>(), It.IsAny<IFetchRequest>(), It.IsAny<CancellationToken>()).Result)
+            .Returns([newMessage.Object]);
+        folder.Setup(f => f.Count).Returns(1);
+        folder.Raise(f => f.CountChanged += null, EventArgs.Empty);
+
+        Assert.True(await task);
+        Assert.Same(newMessage.Object, enumerator.Current);
+
+        cancel.CancelAfter(100);
+        await Assert.ThrowsAnyAsync<OperationCanceledException>(() => enumerator.MoveNextAsync().AsTask());
+    }
+}

server/Mailist/Utilities/ImapClientExtensions.cs

@@ -53,6 +53,7 @@ public static async IAsyncEnumerable<IMessageSummary> IdleFetchAsync(this IImapC
                 }
 
                 messageCount = folder.Count;
+                messagesArrived = false;
             }
         }
         finally