.Net: Integration Tests for Function Calling Stepwise Planner (#4189)

### Motivation and Context / Description

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- The integration tests for Function Calling Stepwise Planner were
removed when we refactored/removed `Planners.Core`. This adds them back
and improves them with more test cases and results validation.
- Also includes a minor fix in sample code (`ChatHistory.AsJson()` no
longer exists)

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

dotnet/samples/KernelSyntaxExamples/Example66_FunctionCallingStepwisePlanner.cs

@@ -34,7 +34,7 @@ public static async Task RunAsync()
             Console.WriteLine($"Q: {question}\nA: {result.FinalAnswer}");
 
             // You can uncomment the line below to see the planner's process for completing the request.
-            // Console.WriteLine($"Chat history:\n{result.ChatHistory?.AsJson()}");
+            // Console.WriteLine($"Chat history:\n{System.Text.Json.JsonSerializer.Serialize(result.ChatHistory)}");
         }
     }
 

dotnet/src/IntegrationTests/IntegrationTests.csproj

@@ -6,7 +6,7 @@
     <RollForward>LatestMajor</RollForward>
     <IsTestProject>true</IsTestProject>
     <IsPackable>false</IsPackable>
-    <NoWarn>CA2007,VSTHRD111,SKEXP0001,SKEXP0002,SKEXP0003,SKEXP0004,SKEXP0010,SKEXP0011,SKEXP0012,SKEXP0020,SKEXP0021,SKEXP0022,SKEXP0023,SKEXP0024,SKEXP0025,SKEXP0026,SKEXP0027,SKEXP0028,SKEXP0029,SKEXP0030,SKEXP0031,SKEXP0032,SKEXP0060</NoWarn>
+    <NoWarn>CA2007,VSTHRD111,SKEXP0001,SKEXP0002,SKEXP0003,SKEXP0004,SKEXP0010,SKEXP0011,SKEXP0012,SKEXP0020,SKEXP0021,SKEXP0022,SKEXP0023,SKEXP0024,SKEXP0025,SKEXP0026,SKEXP0027,SKEXP0028,SKEXP0029,SKEXP0030,SKEXP0031,SKEXP0032,SKEXP0050,SKEXP0054,SKEXP0060,SKEXP0061</NoWarn>
     <UserSecretsId>b7762d10-e29b-4bb1-8b74-b6d69a667dd4</UserSecretsId>
   </PropertyGroup>
   <ItemGroup>

dotnet/src/IntegrationTests/Planners/Stepwise/FunctionCallingStepwisePlannerTests.cs

@@ -0,0 +1,112 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Configuration;
+using Microsoft.SemanticKernel.Planning;
+using Microsoft.SemanticKernel.Plugins.Core;
+using Microsoft.SemanticKernel.Plugins.Web.Bing;
+using Microsoft.SemanticKernel.Plugins.Web;
+using Microsoft.SemanticKernel;
+using SemanticKernel.IntegrationTests.TestSettings;
+using Xunit.Abstractions;
+using Xunit;
+using SemanticKernel.IntegrationTests.Fakes;
+using System.Text.Json;
+
+namespace SemanticKernel.IntegrationTests.Planners.Stepwise;
+public sealed class FunctionCallingStepwisePlannerTests : IDisposable
+{
+    private readonly string _bingApiKey;
+
+    public FunctionCallingStepwisePlannerTests(ITestOutputHelper output)
+    {
+        this._testOutputHelper = new RedirectOutput(output);
+
+        // Load configuration
+        this._configuration = new ConfigurationBuilder()
+            .AddJsonFile(path: "testsettings.json", optional: false, reloadOnChange: true)
+            .AddJsonFile(path: "testsettings.development.json", optional: true, reloadOnChange: true)
+            .AddEnvironmentVariables()
+            .AddUserSecrets<FunctionCallingStepwisePlannerTests>()
+            .Build();
+
+        string? bingApiKeyCandidate = this._configuration["Bing:ApiKey"];
+        Assert.NotNull(bingApiKeyCandidate);
+        this._bingApiKey = bingApiKeyCandidate;
+    }
+
+    [Theory(Skip = "Requires model deployment that supports function calling.")]
+    [InlineData("What is the tallest mountain on Earth? How tall is it?", "Everest", new string[] { "WebSearch_Search" })]
+    [InlineData("What is the weather in Seattle?", "Seattle", new string[] { "WebSearch_Search" })]
+    [InlineData("What is the current hour number, plus 5?", "", new string[] { "Time_HourNumber", "Math_Add" })]
+    [InlineData("What is 387 minus 22? Email the solution to John and Mary.", "365", new string[] { "Math_Subtract", "Email_GetEmailAddress", "Email_SendEmail" })]
+    public async Task CanExecuteStepwisePlanAsync(string prompt, string partialExpectedAnswer, string[] expectedFunctions)
+    {
+        // Arrange
+        Kernel kernel = this.InitializeKernel();
+        var bingConnector = new BingConnector(this._bingApiKey);
+        var webSearchEnginePlugin = new WebSearchEnginePlugin(bingConnector);
+        kernel.ImportPluginFromObject(webSearchEnginePlugin, "WebSearch");
+        kernel.ImportPluginFromType<TimePlugin>("Time");
+        kernel.ImportPluginFromType<MathPlugin>("Math");
+        kernel.ImportPluginFromType<EmailPluginFake>("Email");
+
+        var planner = new FunctionCallingStepwisePlanner(
+            new FunctionCallingStepwisePlannerConfig() { MaxIterations = 10 });
+
+        // Act
+        var planResult = await planner.ExecuteAsync(kernel, prompt);
+
+        // Assert - should contain the expected answer & function calls within the maximum iterations
+        Assert.NotNull(planResult);
+        Assert.NotEqual(string.Empty, planResult.FinalAnswer);
+        Assert.True(planResult.Iterations > 0);
+        Assert.True(planResult.Iterations <= 10);
+        Assert.Contains(partialExpectedAnswer, planResult.FinalAnswer, StringComparison.InvariantCultureIgnoreCase);
+
+        string serializedChatHistory = JsonSerializer.Serialize(planResult.ChatHistory);
+        foreach (string expectedFunction in expectedFunctions)
+        {
+            Assert.Contains(expectedFunction, serializedChatHistory, StringComparison.InvariantCultureIgnoreCase);
+        }
+    }
+
+    private Kernel InitializeKernel()
+    {
+        AzureOpenAIConfiguration? azureOpenAIConfiguration = this._configuration.GetSection("AzureOpenAI").Get<AzureOpenAIConfiguration>();
+        Assert.NotNull(azureOpenAIConfiguration);
+
+        IKernelBuilder builder = Kernel.CreateBuilder()
+            .AddAzureOpenAIChatCompletion(
+                deploymentName: azureOpenAIConfiguration.ChatDeploymentName!,
+                endpoint: azureOpenAIConfiguration.Endpoint,
+                apiKey: azureOpenAIConfiguration.ApiKey);
+
+        var kernel = builder.Build();
+
+        return kernel;
+    }
+
+    private readonly RedirectOutput _testOutputHelper;
+    private readonly IConfigurationRoot _configuration;
+
+    public void Dispose()
+    {
+        this.Dispose(true);
+        GC.SuppressFinalize(this);
+    }
+
+    ~FunctionCallingStepwisePlannerTests()
+    {
+        this.Dispose(false);
+    }
+
+    private void Dispose(bool disposing)
+    {
+        if (disposing)
+        {
+            this._testOutputHelper.Dispose();
+        }
+    }
+}