chore: import upstream snapshot with attribution

dotnet/tests/Microsoft.Agents.AI.UnitTests/Compaction/ChatReducerCompactionStrategyTests.cs

@@ -0,0 +1,255 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Agents.AI.Compaction;
+using Microsoft.Extensions.AI;
+
+namespace Microsoft.Agents.AI.UnitTests.Compaction;
+
+/// <summary>
+/// Contains tests for the <see cref="ChatReducerCompactionStrategy"/> class.
+/// </summary>
+public class ChatReducerCompactionStrategyTests
+{
+    [Fact]
+    public void ConstructorNullReducerThrows()
+    {
+        // Act & Assert
+        Assert.Throws<ArgumentNullException>(() => new ChatReducerCompactionStrategy(null!, CompactionTriggers.Always));
+    }
+
+    [Fact]
+    public async Task CompactAsyncTriggerNotMetReturnsFalseAsync()
+    {
+        // Arrange — trigger never fires
+        TestChatReducer reducer = new(messages => messages.Take(1));
+        ChatReducerCompactionStrategy strategy = new(reducer, CompactionTriggers.Never);
+        CompactionMessageIndex index = CompactionMessageIndex.Create(
+        [
+            new ChatMessage(ChatRole.User, "Hello"),
+            new ChatMessage(ChatRole.Assistant, "Hi!"),
+        ]);
+
+        // Act
+        bool result = await strategy.CompactAsync(index);
+
+        // Assert
+        Assert.False(result);
+        Assert.Equal(0, reducer.CallCount);
+        Assert.Equal(2, index.IncludedGroupCount);
+    }
+
+    [Fact]
+    public async Task CompactAsyncReducerReturnsFewerMessagesRebuildsIndexAsync()
+    {
+        // Arrange — reducer keeps only the last message
+        TestChatReducer reducer = new(messages => messages.Skip(messages.Count() - 1));
+        ChatReducerCompactionStrategy strategy = new(reducer, CompactionTriggers.Always);
+        CompactionMessageIndex index = CompactionMessageIndex.Create(
+        [
+            new ChatMessage(ChatRole.User, "First"),
+            new ChatMessage(ChatRole.Assistant, "Response 1"),
+            new ChatMessage(ChatRole.User, "Second"),
+        ]);
+
+        // Act
+        bool result = await strategy.CompactAsync(index);
+
+        // Assert
+        Assert.True(result);
+        Assert.Equal(1, reducer.CallCount);
+        Assert.Equal(1, index.IncludedGroupCount);
+        Assert.Equal("Second", index.Groups[0].Messages[0].Text);
+    }
+
+    [Fact]
+    public async Task CompactAsyncReducerReturnsSameCountReturnsFalseAsync()
+    {
+        // Arrange — reducer returns all messages (no reduction)
+        TestChatReducer reducer = new(messages => messages);
+        ChatReducerCompactionStrategy strategy = new(reducer, CompactionTriggers.Always);
+        CompactionMessageIndex index = CompactionMessageIndex.Create(
+        [
+            new ChatMessage(ChatRole.User, "Hello"),
+            new ChatMessage(ChatRole.Assistant, "Hi!"),
+        ]);
+
+        // Act
+        bool result = await strategy.CompactAsync(index);
+
+        // Assert
+        Assert.False(result);
+        Assert.Equal(1, reducer.CallCount);
+        Assert.Equal(2, index.IncludedGroupCount);
+    }
+
+    [Fact]
+    public async Task CompactAsyncEmptyIndexReturnsFalseAsync()
+    {
+        // Arrange — no included messages
+        TestChatReducer reducer = new(messages => messages);
+        ChatReducerCompactionStrategy strategy = new(reducer, CompactionTriggers.Always);
+        CompactionMessageIndex index = CompactionMessageIndex.Create([]);
+
+        // Act
+        bool result = await strategy.CompactAsync(index);
+
+        // Assert
+        Assert.False(result);
+        Assert.Equal(0, reducer.CallCount);
+    }
+
+    [Fact]
+    public async Task CompactAsyncPreservesSystemMessagesWhenReducerKeepsThemAsync()
+    {
+        // Arrange — reducer keeps system + last user message
+        TestChatReducer reducer = new(messages =>
+        {
+            var nonSystem = messages.Where(m => m.Role != ChatRole.System).ToList();
+            return messages.Where(m => m.Role == ChatRole.System)
+                .Concat(nonSystem.Skip(nonSystem.Count - 1));
+        });
+
+        ChatReducerCompactionStrategy strategy = new(reducer, CompactionTriggers.Always);
+        CompactionMessageIndex index = CompactionMessageIndex.Create(
+        [
+            new ChatMessage(ChatRole.System, "You are helpful."),
+            new ChatMessage(ChatRole.User, "First"),
+            new ChatMessage(ChatRole.Assistant, "Response 1"),
+            new ChatMessage(ChatRole.User, "Second"),
+        ]);
+
+        // Act
+        bool result = await strategy.CompactAsync(index);
+
+        // Assert
+        Assert.True(result);
+        Assert.Equal(2, index.IncludedGroupCount);
+        Assert.Equal(CompactionGroupKind.System, index.Groups[0].Kind);
+        Assert.Equal("You are helpful.", index.Groups[0].Messages[0].Text);
+        Assert.Equal(CompactionGroupKind.User, index.Groups[1].Kind);
+        Assert.Equal("Second", index.Groups[1].Messages[0].Text);
+    }
+
+    [Fact]
+    public async Task CompactAsyncRebuildsToolCallGroupsCorrectlyAsync()
+    {
+        // Arrange — reducer keeps last 3 messages (assistant tool call + tool result + user)
+        TestChatReducer reducer = new(messages => messages.Skip(messages.Count() - 3));
+
+        ChatMessage assistantToolCall = new(ChatRole.Assistant, [new FunctionCallContent("call1", "get_weather")]);
+        ChatMessage toolResult = new(ChatRole.Tool, "Sunny");
+
+        ChatReducerCompactionStrategy strategy = new(reducer, CompactionTriggers.Always);
+        CompactionMessageIndex index = CompactionMessageIndex.Create(
+        [
+            new ChatMessage(ChatRole.User, "Old question"),
+            new ChatMessage(ChatRole.Assistant, "Old answer"),
+            assistantToolCall,
+            toolResult,
+            new ChatMessage(ChatRole.User, "New question"),
+        ]);
+
+        // Act
+        bool result = await strategy.CompactAsync(index);
+
+        // Assert
+        Assert.True(result);
+        // Should have 2 groups: ToolCall group (assistant + tool result) + User group
+        Assert.Equal(2, index.IncludedGroupCount);
+        Assert.Equal(CompactionGroupKind.ToolCall, index.Groups[0].Kind);
+        Assert.Equal(2, index.Groups[0].Messages.Count);
+        Assert.Equal(CompactionGroupKind.User, index.Groups[1].Kind);
+    }
+
+    [Fact]
+    public async Task CompactAsyncSkipsAlreadyExcludedGroupsAsync()
+    {
+        // Arrange — one group is pre-excluded, reducer keeps last message
+        TestChatReducer reducer = new(messages => messages.Skip(messages.Count() - 1));
+        ChatReducerCompactionStrategy strategy = new(reducer, CompactionTriggers.Always);
+        CompactionMessageIndex index = CompactionMessageIndex.Create(
+        [
+            new ChatMessage(ChatRole.User, "Excluded"),
+            new ChatMessage(ChatRole.User, "Included 1"),
+            new ChatMessage(ChatRole.User, "Included 2"),
+        ]);
+        index.Groups[0].IsExcluded = true;
+
+        // Act
+        bool result = await strategy.CompactAsync(index);
+
+        // Assert — reducer only saw 2 included messages, kept 1
+        Assert.True(result);
+        Assert.Equal(1, index.IncludedGroupCount);
+        Assert.Equal("Included 2", index.Groups[0].Messages[0].Text);
+    }
+
+    [Fact]
+    public async Task CompactAsyncExposesReducerPropertyAsync()
+    {
+        // Arrange
+        TestChatReducer reducer = new(messages => messages);
+        ChatReducerCompactionStrategy strategy = new(reducer, CompactionTriggers.Always);
+
+        // Assert
+        Assert.Same(reducer, strategy.ChatReducer);
+        await Task.CompletedTask;
+    }
+
+    [Fact]
+    public async Task CompactAsyncPassesCancellationTokenToReducerAsync()
+    {
+        // Arrange
+        using CancellationTokenSource cancellationSource = new();
+        CancellationToken capturedToken = default;
+        TestChatReducer reducer = new((messages, cancellationToken) =>
+        {
+            capturedToken = cancellationToken;
+            return Task.FromResult<IEnumerable<ChatMessage>>(messages.Skip(messages.Count() - 1).ToList());
+        });
+
+        ChatReducerCompactionStrategy strategy = new(reducer, CompactionTriggers.Always);
+        CompactionMessageIndex index = CompactionMessageIndex.Create(
+        [
+            new ChatMessage(ChatRole.User, "First"),
+            new ChatMessage(ChatRole.User, "Second"),
+        ]);
+
+        // Act
+        await strategy.CompactAsync(index, logger: null, cancellationSource.Token);
+
+        // Assert
+        Assert.Equal(cancellationSource.Token, capturedToken);
+    }
+
+    /// <summary>
+    /// A test implementation of <see cref="IChatReducer"/> that applies a configurable reduction function.
+    /// </summary>
+    private sealed class TestChatReducer : IChatReducer
+    {
+        private readonly Func<IEnumerable<ChatMessage>, CancellationToken, Task<IEnumerable<ChatMessage>>> _reduceFunc;
+
+        public TestChatReducer(Func<IEnumerable<ChatMessage>, IEnumerable<ChatMessage>> reduceFunc)
+        {
+            this._reduceFunc = (messages, _) => Task.FromResult(reduceFunc(messages));
+        }
+
+        public TestChatReducer(Func<IEnumerable<ChatMessage>, CancellationToken, Task<IEnumerable<ChatMessage>>> reduceFunc)
+        {
+            this._reduceFunc = reduceFunc;
+        }
+
+        public int CallCount { get; private set; }
+
+        public async Task<IEnumerable<ChatMessage>> ReduceAsync(IEnumerable<ChatMessage> messages, CancellationToken cancellationToken = default)
+        {
+            this.CallCount++;
+            return await this._reduceFunc(messages, cancellationToken).ConfigureAwait(false);
+        }
+    }
+}