diff --git a/tests/SimpleBranchVersioning.Tests/AppVersionGeneratorIntegrationTests.cs b/tests/SimpleBranchVersioning.Tests/AppVersionGeneratorIntegrationTests.cs
new file mode 100644
index 0000000..21a26bf
--- /dev/null
+++ b/tests/SimpleBranchVersioning.Tests/AppVersionGeneratorIntegrationTests.cs
@@ -0,0 +1,256 @@
+using SimpleBranchVersioning.Tests.Helpers;
+
+namespace SimpleBranchVersioning.Tests;
+
+/// <summary>
+/// Integration tests for AppVersionGenerator that test real file I/O paths.
+/// These tests create actual git directory structures on disk.
+/// </summary>
+public class AppVersionGeneratorIntegrationTests
+{
+    private const string MinimalSource = """
+        namespace TestApp;
+        public class Program { }
+        """;
+
+    #region ParseGitInfo Integration Tests
+
+    [Test]
+    public async Task Generator_WithRealGitDirectory_ReadsCommitFromRefsHeads()
+    {
+        // Arrange
+        string tempDir = CreateTempDirectory();
+        try
+        {
+            string gitDir = Path.Combine(tempDir, ".git");
+            Directory.CreateDirectory(gitDir);
+            Directory.CreateDirectory(Path.Combine(gitDir, "refs", "heads"));
+
+            // Create HEAD file pointing to a branch
+            string headPath = Path.Combine(gitDir, "HEAD");
+            await File.WriteAllTextAsync(headPath, "ref: refs/heads/main\n");
+
+            // Create refs/heads/main with a commit hash
+            string refPath = Path.Combine(gitDir, "refs", "heads", "main");
+            await File.WriteAllTextAsync(refPath, "abc1234def5678901234567890123456789012345\n");
+
+            // Act
+            var result = GeneratorTestHelper.RunGeneratorWithGitDirectory(
+                MinimalSource,
+                headPath);
+
+            string generatedSource = result.GetRequiredGeneratedSource("AppVersion.g.cs");
+
+            // Assert
+            await Assert.That(generatedSource).Contains("""Branch = "main""");
+            await Assert.That(generatedSource).Contains("""CommitId = "abc1234""");
+        }
+        finally
+        {
+            DeleteTempDirectory(tempDir);
+        }
+    }
+
+    [Test]
+    public async Task Generator_WithRealGitDirectory_ReadsCommitFromNestedBranch()
+    {
+        // Arrange
+        string tempDir = CreateTempDirectory();
+        try
+        {
+            string gitDir = Path.Combine(tempDir, ".git");
+            Directory.CreateDirectory(gitDir);
+            Directory.CreateDirectory(Path.Combine(gitDir, "refs", "heads", "feature"));
+
+            // Create HEAD file pointing to a nested branch
+            string headPath = Path.Combine(gitDir, "HEAD");
+            await File.WriteAllTextAsync(headPath, "ref: refs/heads/feature/login\n");
+
+            // Create refs/heads/feature/login with a commit hash
+            string refPath = Path.Combine(gitDir, "refs", "heads", "feature", "login");
+            await File.WriteAllTextAsync(refPath, "def5678abc1234567890123456789012345678901\n");
+
+            // Act
+            var result = GeneratorTestHelper.RunGeneratorWithGitDirectory(
+                MinimalSource,
+                headPath);
+
+            string generatedSource = result.GetRequiredGeneratedSource("AppVersion.g.cs");
+
+            // Assert
+            await Assert.That(generatedSource).Contains("""Branch = "feature/login""");
+            await Assert.That(generatedSource).Contains("""CommitId = "def5678""");
+        }
+        finally
+        {
+            DeleteTempDirectory(tempDir);
+        }
+    }
+
+    [Test]
+    public async Task Generator_WithRealGitDirectory_HandlesDetachedHead()
+    {
+        // Arrange
+        string tempDir = CreateTempDirectory();
+        try
+        {
+            string gitDir = Path.Combine(tempDir, ".git");
+            Directory.CreateDirectory(gitDir);
+
+            // Create HEAD file with a direct commit hash (detached HEAD)
+            string headPath = Path.Combine(gitDir, "HEAD");
+            await File.WriteAllTextAsync(headPath, "9876543210abcdef1234567890abcdef12345678\n");
+
+            // Act
+            var result = GeneratorTestHelper.RunGeneratorWithGitDirectory(
+                MinimalSource,
+                headPath);
+
+            string generatedSource = result.GetRequiredGeneratedSource("AppVersion.g.cs");
+
+            // Assert
+            await Assert.That(generatedSource).Contains("""Branch = "detached""");
+            await Assert.That(generatedSource).Contains("""CommitId = "9876543""");
+        }
+        finally
+        {
+            DeleteTempDirectory(tempDir);
+        }
+    }
+
+    [Test]
+    public async Task Generator_WithRealGitDirectory_MissingRefFile_UsesBranchWithoutCommitId()
+    {
+        // Arrange
+        string tempDir = CreateTempDirectory();
+        try
+        {
+            string gitDir = Path.Combine(tempDir, ".git");
+            Directory.CreateDirectory(gitDir);
+            Directory.CreateDirectory(Path.Combine(gitDir, "refs", "heads"));
+
+            // Create HEAD file pointing to a branch
+            string headPath = Path.Combine(gitDir, "HEAD");
+            await File.WriteAllTextAsync(headPath, "ref: refs/heads/main\n");
+
+            // Note: NOT creating refs/heads/main file - simulates missing ref
+
+            // Act
+            var result = GeneratorTestHelper.RunGeneratorWithGitDirectory(
+                MinimalSource,
+                headPath);
+
+            string generatedSource = result.GetRequiredGeneratedSource("AppVersion.g.cs");
+
+            // Assert - branch is extracted but commit ID falls back to "0000000"
+            await Assert.That(generatedSource).Contains("""Branch = "main""");
+            await Assert.That(generatedSource).Contains("""CommitId = "0000000""");
+        }
+        finally
+        {
+            DeleteTempDirectory(tempDir);
+        }
+    }
+
+    [Test]
+    public async Task Generator_WithRealGitDirectory_ShortCommitHash_UsesBranchWithoutCommitId()
+    {
+        // Arrange
+        string tempDir = CreateTempDirectory();
+        try
+        {
+            string gitDir = Path.Combine(tempDir, ".git");
+            Directory.CreateDirectory(gitDir);
+            Directory.CreateDirectory(Path.Combine(gitDir, "refs", "heads"));
+
+            // Create HEAD file pointing to a branch
+            string headPath = Path.Combine(gitDir, "HEAD");
+            await File.WriteAllTextAsync(headPath, "ref: refs/heads/main\n");
+
+            // Create refs/heads/main with a too-short commit hash (< 7 chars)
+            string refPath = Path.Combine(gitDir, "refs", "heads", "main");
+            await File.WriteAllTextAsync(refPath, "abc12\n");
+
+            // Act
+            var result = GeneratorTestHelper.RunGeneratorWithGitDirectory(
+                MinimalSource,
+                headPath);
+
+            string generatedSource = result.GetRequiredGeneratedSource("AppVersion.g.cs");
+
+            // Assert - branch is extracted but commit ID falls back to "0000000" due to short hash
+            await Assert.That(generatedSource).Contains("""Branch = "main""");
+            await Assert.That(generatedSource).Contains("""CommitId = "0000000""");
+        }
+        finally
+        {
+            DeleteTempDirectory(tempDir);
+        }
+    }
+
+    [Test]
+    public async Task Generator_WithRealGitDirectory_ReleaseBranch_ExtractsVersion()
+    {
+        // Arrange
+        string tempDir = CreateTempDirectory();
+        try
+        {
+            string gitDir = Path.Combine(tempDir, ".git");
+            Directory.CreateDirectory(gitDir);
+            Directory.CreateDirectory(Path.Combine(gitDir, "refs", "heads", "release"));
+
+            // Create HEAD file pointing to a release branch
+            string headPath = Path.Combine(gitDir, "HEAD");
+            await File.WriteAllTextAsync(headPath, "ref: refs/heads/release/v1.2.3\n");
+
+            // Create refs/heads/release/v1.2.3 with a commit hash
+            string refPath = Path.Combine(gitDir, "refs", "heads", "release", "v1.2.3");
+            await File.WriteAllTextAsync(refPath, "abc1234def5678901234567890123456789012345\n");
+
+            // Act
+            var result = GeneratorTestHelper.RunGeneratorWithGitDirectory(
+                MinimalSource,
+                headPath);
+
+            string generatedSource = result.GetRequiredGeneratedSource("AppVersion.g.cs");
+
+            // Assert
+            await Assert.That(generatedSource).Contains("""Branch = "release/v1.2.3""");
+            await Assert.That(generatedSource).Contains("""Version = "1.2.3""");
+            await Assert.That(generatedSource).Contains("""CommitId = "abc1234""");
+            await Assert.That(generatedSource).Contains("""PackageVersion = "1.2.3+abc1234""");
+        }
+        finally
+        {
+            DeleteTempDirectory(tempDir);
+        }
+    }
+
+    #endregion
+
+    #region Helper Methods
+
+    private static string CreateTempDirectory()
+    {
+        string tempDir = Path.Combine(Path.GetTempPath(), $"sbv-test-{Guid.NewGuid():N}");
+        Directory.CreateDirectory(tempDir);
+        return tempDir;
+    }
+
+    private static void DeleteTempDirectory(string tempDir)
+    {
+        try
+        {
+            if (Directory.Exists(tempDir))
+            {
+                Directory.Delete(tempDir, recursive: true);
+            }
+        }
+        catch
+        {
+            // Ignore cleanup errors in tests
+        }
+    }
+
+    #endregion
+}
diff --git a/tests/SimpleBranchVersioning.Tests/Helpers/FileBasedAdditionalText.cs b/tests/SimpleBranchVersioning.Tests/Helpers/FileBasedAdditionalText.cs
new file mode 100644
index 0000000..b19ee75
--- /dev/null
+++ b/tests/SimpleBranchVersioning.Tests/Helpers/FileBasedAdditionalText.cs
@@ -0,0 +1,24 @@
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Text;
+
+namespace SimpleBranchVersioning.Tests.Helpers;
+
+/// <summary>
+/// File-based implementation of AdditionalText for integration tests.
+/// Reads content from actual files on disk.
+/// </summary>
+public sealed class FileBasedAdditionalText(string filePath) : AdditionalText
+{
+    public override string Path => filePath;
+
+    public override SourceText? GetText(CancellationToken cancellationToken = default)
+    {
+        if (!File.Exists(filePath))
+        {
+            return null;
+        }
+
+        string content = File.ReadAllText(filePath);
+        return SourceText.From(content);
+    }
+}
diff --git a/tests/SimpleBranchVersioning.Tests/Helpers/GeneratorTestHelper.cs b/tests/SimpleBranchVersioning.Tests/Helpers/GeneratorTestHelper.cs
index 0d4f480..34d0f99 100644
--- a/tests/SimpleBranchVersioning.Tests/Helpers/GeneratorTestHelper.cs
+++ b/tests/SimpleBranchVersioning.Tests/Helpers/GeneratorTestHelper.cs
@@ -63,6 +63,56 @@ public static GeneratorTestResult RunGenerator(
             driver.GetRunResult());
     }
 
+    /// <summary>
+    /// Runs the AppVersionGenerator with a real git directory structure for integration testing.
+    /// This allows testing the file I/O paths in ParseGitInfo.
+    /// </summary>
+    public static GeneratorTestResult RunGeneratorWithGitDirectory(
+        string sourceCode,
+        string gitHeadFilePath,
+        string? rootNamespace = null,
+        bool includeCommitIdMetadata = true,
+        bool generateVersionFile = false,
+        bool setPackageVersionFromBranch = true)
+    {
+        var syntaxTree = CSharpSyntaxTree.ParseText(sourceCode);
+
+        // Use Basic.Reference.Assemblies for compilation references
+        var compilation = CSharpCompilation.Create(
+            assemblyName: "TestAssembly",
+            syntaxTrees: [syntaxTree],
+            references: Basic.Reference.Assemblies.Net80.References.All,
+            options: new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary));
+
+        // Build editorconfig content for global options
+        string editorConfig = BuildEditorConfig(
+            branchOverride: null,
+            rootNamespace,
+            includeCommitIdMetadata,
+            generateVersionFile,
+            setPackageVersionFromBranch);
+
+        // Create additional texts using the real file path
+        ImmutableArray<AdditionalText> additionalTexts = [new FileBasedAdditionalText(gitHeadFilePath)];
+
+        // Configure driver with options
+        GeneratorDriver driver = CSharpGeneratorDriver.Create(
+            generators: [new AppVersionGenerator().AsSourceGenerator()],
+            additionalTexts: additionalTexts,
+            parseOptions: (CSharpParseOptions)syntaxTree.Options,
+            optionsProvider: new TestAnalyzerConfigOptionsProvider(editorConfig));
+
+        driver = driver.RunGeneratorsAndUpdateCompilation(
+            compilation,
+            out var outputCompilation,
+            out var diagnostics);
+
+        return new GeneratorTestResult(
+            outputCompilation,
+            diagnostics,
+            driver.GetRunResult());
+    }
+
     private static string BuildEditorConfig(
         string? branchOverride,
         string? rootNamespace,