refactor(tests): DRY up test infrastructure

- Extract TestListingSourceCodeServiceHelper with ResolveTestDataPath() and CreateService()
  so both ListingSourceCodeServiceTests and WebApplicationFactory share the same TestData-backed
  ListingSourceCodeService setup. Also aligns failure behavior: both now throw a clear
  InvalidOperationException if the TestData directory is missing.
- Add SetupSearch() helper in AISearchServiceTests that returns the ISetup for SearchAsync,
  removing the repeated 5-line Moq matcher block from all 4 test bodies. Each test still
  specifies its own .Returns(...) inline so retry behavior stays visible.

Author: BenjaminMichaelis

EssentialCSharp.Chat.Tests/AISearchServiceTests.cs

@@ -4,6 +4,7 @@
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.VectorData;
 using Moq;
+using Moq.Language.Flow;
 using Npgsql;
 
 namespace EssentialCSharp.Chat.Tests;
@@ -44,19 +45,21 @@ private static async IAsyncEnumerable<VectorSearchResult<BookContentChunk>> OneR
         await Task.CompletedTask;
     }
 
+    private static ISetup<VectorStoreCollection<string, BookContentChunk>, IAsyncEnumerable<VectorSearchResult<BookContentChunk>>>
+        SetupSearch(Mock<VectorStoreCollection<string, BookContentChunk>> mock) =>
+            mock.Setup(c => c.SearchAsync(
+                It.IsAny<ReadOnlyMemory<float>>(),
+                It.IsAny<int>(),
+                It.IsAny<VectorSearchOptions<BookContentChunk>?>(),
+                It.IsAny<CancellationToken>()));
+
     [Test]
     public async Task ExecuteVectorSearch_HappyPath_ReturnsResultsWithoutRetry()
     {
         var (svc, collectionMock) = CreateService();
         int callCount = 0;
 
-        collectionMock
-            .Setup(c => c.SearchAsync(
-                It.IsAny<ReadOnlyMemory<float>>(),
-                It.IsAny<int>(),
-                It.IsAny<VectorSearchOptions<BookContentChunk>?>(),
-                It.IsAny<CancellationToken>()))
-            .Returns(() => { callCount++; return OneResultStream(); });
+        SetupSearch(collectionMock).Returns(() => { callCount++; return OneResultStream(); });
 
         var results = await svc.ExecuteVectorSearch("test query");
 
@@ -70,19 +73,13 @@ public async Task ExecuteVectorSearch_RetriesOnce_WhenFirstAttemptThrows28000()
         var (svc, collectionMock) = CreateService();
         int callCount = 0;
 
-        collectionMock
-            .Setup(c => c.SearchAsync(
-                It.IsAny<ReadOnlyMemory<float>>(),
-                It.IsAny<int>(),
-                It.IsAny<VectorSearchOptions<BookContentChunk>?>(),
-                It.IsAny<CancellationToken>()))
-            .Returns(() =>
-            {
-                callCount++;
-                if (callCount == 1)
-                    throw new PostgresException("auth token expired", "FATAL", "FATAL", "28000");
-                return OneResultStream();
-            });
+        SetupSearch(collectionMock).Returns(() =>
+        {
+            callCount++;
+            if (callCount == 1)
+                throw new PostgresException("auth token expired", "FATAL", "FATAL", "28000");
+            return OneResultStream();
+        });
 
         var results = await svc.ExecuteVectorSearch("test query");
 
@@ -95,13 +92,7 @@ public async Task ExecuteVectorSearch_DoesNotRetry_WhenSqlStateIsNot28000()
     {
         var (svc, collectionMock) = CreateService();
 
-        collectionMock
-            .Setup(c => c.SearchAsync(
-                It.IsAny<ReadOnlyMemory<float>>(),
-                It.IsAny<int>(),
-                It.IsAny<VectorSearchOptions<BookContentChunk>?>(),
-                It.IsAny<CancellationToken>()))
-            .Returns(() => throw new PostgresException("table not found", "ERROR", "ERROR", "42P01"));
+        SetupSearch(collectionMock).Returns(() => throw new PostgresException("table not found", "ERROR", "ERROR", "42P01"));
 
         await Assert.ThrowsAsync<PostgresException>(() => svc.ExecuteVectorSearch("test query"));
     }
@@ -111,13 +102,7 @@ public async Task ExecuteVectorSearch_PropagatesException_WhenBothAttemptsFail28
     {
         var (svc, collectionMock) = CreateService();
 
-        collectionMock
-            .Setup(c => c.SearchAsync(
-                It.IsAny<ReadOnlyMemory<float>>(),
-                It.IsAny<int>(),
-                It.IsAny<VectorSearchOptions<BookContentChunk>?>(),
-                It.IsAny<CancellationToken>()))
-            .Returns(() => throw new PostgresException("auth failed", "FATAL", "FATAL", "28000"));
+        SetupSearch(collectionMock).Returns(() => throw new PostgresException("auth failed", "FATAL", "FATAL", "28000"));
 
         await Assert.ThrowsAsync<PostgresException>(() => svc.ExecuteVectorSearch("test query"));
     }

EssentialCSharp.Web.Tests/ListingSourceCodeServiceTests.cs

@@ -1,9 +1,5 @@
 using EssentialCSharp.Web.Models;
 using EssentialCSharp.Web.Services;
-using Microsoft.AspNetCore.Hosting;
-using Microsoft.Extensions.FileProviders;
-using Moq;
-using Moq.AutoMock;
 
 namespace EssentialCSharp.Web.Tests;
 
@@ -130,30 +126,6 @@ public async Task GetListingsByChapterAsync_WithInvalidChapter_ReturnsEmptyList(
         await Assert.That(results).IsEmpty();
     }
 
-    private static ListingSourceCodeService CreateService()
-    {
-        DirectoryInfo testDataRoot = GetTestDataPath();
-
-        AutoMocker mocker = new();
-        Mock<IWebHostEnvironment> mockWebHostEnvironment = mocker.GetMock<IWebHostEnvironment>();
-        mockWebHostEnvironment.Setup(m => m.ContentRootPath).Returns(testDataRoot.FullName);
-        mockWebHostEnvironment.Setup(m => m.ContentRootFileProvider).Returns(new PhysicalFileProvider(testDataRoot.FullName));
-
-        return mocker.CreateInstance<ListingSourceCodeService>();
-    }
-
-    private static DirectoryInfo GetTestDataPath()
-    {
-        string baseDirectory = AppContext.BaseDirectory;
-        string testDataPath = Path.Join(baseDirectory, "TestData");
-        
-        DirectoryInfo testDataDirectory = new(testDataPath);
-        
-        if (!testDataDirectory.Exists)
-        {
-            throw new InvalidOperationException($"TestData directory not found at: {testDataDirectory.FullName}");
-        }
-        
-        return testDataDirectory;
-    }
+    private static ListingSourceCodeService CreateService() =>
+        TestListingSourceCodeServiceHelper.CreateService();
 }

EssentialCSharp.Web.Tests/TestListingSourceCodeServiceHelper.cs

@@ -0,0 +1,29 @@
+using EssentialCSharp.Web.Services;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.FileProviders;
+using Moq.AutoMock;
+
+namespace EssentialCSharp.Web.Tests;
+
+internal static class TestListingSourceCodeServiceHelper
+{
+    internal static string ResolveTestDataPath()
+    {
+        string testDataPath = Path.Join(AppContext.BaseDirectory, "TestData");
+        if (!Directory.Exists(testDataPath))
+            throw new InvalidOperationException($"TestData directory not found at: {testDataPath}");
+        return testDataPath;
+    }
+
+    internal static ListingSourceCodeService CreateService()
+    {
+        string testDataPath = ResolveTestDataPath();
+
+        AutoMocker mocker = new();
+        mocker.Setup<IWebHostEnvironment, string>(m => m.ContentRootPath).Returns(testDataPath);
+        mocker.Setup<IWebHostEnvironment, IFileProvider>(m => m.ContentRootFileProvider)
+              .Returns(new PhysicalFileProvider(testDataPath));
+
+        return mocker.CreateInstance<ListingSourceCodeService>();
+    }
+}

EssentialCSharp.Web.Tests/WebApplicationFactory.cs

@@ -9,8 +9,6 @@
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
-using Microsoft.Extensions.FileProviders;
-using Moq.AutoMock;
 
 namespace EssentialCSharp.Web.Tests;
 
@@ -77,16 +75,8 @@ protected override void ConfigureWebHost(IWebHostBuilder builder)
 
             // Replace IListingSourceCodeService with one backed by TestData
             services.RemoveAll<IListingSourceCodeService>();
-
-            string testDataPath = Path.Join(AppContext.BaseDirectory, "TestData");
-            var fileProvider = new PhysicalFileProvider(testDataPath);
-            services.AddSingleton<IListingSourceCodeService>(sp =>
-            {
-                var mocker = new AutoMocker();
-                mocker.Setup<IWebHostEnvironment, string>(m => m.ContentRootPath).Returns(testDataPath);
-                mocker.Setup<IWebHostEnvironment, IFileProvider>(m => m.ContentRootFileProvider).Returns(fileProvider);
-                return mocker.CreateInstance<ListingSourceCodeService>();
-            });
+            services.AddSingleton<IListingSourceCodeService>(
+                _ => TestListingSourceCodeServiceHelper.CreateService());
         });
     }