Reuse PortAllocation worktree candidate list in tests via InternalsVisibleTo

Author: tjementum

application/shared-kernel/SharedKernel/Configuration/PortAllocation.cs

@@ -17,7 +17,7 @@ public sealed record PortAllocation(int BasePort)
     private const string PortFileName = "port.txt";
 
     // Worktrees scan these in order and pick the first base port whose full allocation is free.
-    private static readonly int[] WorktreeCandidateBasePorts = [9100, 9200, 9300, 9400, 9500, 9600, 9700, 9800, 9900];
+    internal static readonly int[] WorktreeCandidateBasePorts = [9100, 9200, 9300, 9400, 9500, 9600, 9700, 9800, 9900];
 
     public int AppGateway => BasePort;
 

application/shared-kernel/SharedKernel/SharedKernel.csproj

@@ -60,4 +60,8 @@
         <EmbeddedResource Include="Platform\platform-settings.jsonc"/>
     </ItemGroup>
 
+    <ItemGroup>
+        <InternalsVisibleTo Include="SharedKernel.Tests"/>
+    </ItemGroup>
+
 </Project>

application/shared-kernel/Tests/Configuration/PortAllocationTests.cs

@@ -0,0 +1,50 @@
+using FluentAssertions;
+using SharedKernel.Configuration;
+using Xunit;
+
+namespace SharedKernel.Tests.Configuration;
+
+public sealed class PortAllocationTests : IDisposable
+{
+    private const int DefaultBasePort = 9000;
+
+    private readonly string _temporaryDirectory = Path.Combine(Path.GetTempPath(), $"PortAllocationTests-{Guid.NewGuid():N}");
+
+    public PortAllocationTests()
+    {
+        Directory.CreateDirectory(_temporaryDirectory);
+    }
+
+    public void Dispose()
+    {
+        if (Directory.Exists(_temporaryDirectory)) Directory.Delete(_temporaryDirectory, true);
+    }
+
+    [Fact]
+    public void LoadFrom_WhenPortFileMissingAndGitIsFile_ShouldPickFreeWorktreeCandidate()
+    {
+        // Arrange: a worktree has `.git` as a FILE (not a directory)
+        File.WriteAllText(Path.Combine(_temporaryDirectory, ".git"), "gitdir: /some/other/path");
+
+        // Act
+        var allocation = PortAllocation.LoadFrom(_temporaryDirectory);
+
+        // Assert
+        PortAllocation.WorktreeCandidateBasePorts.Should().Contain(allocation.BasePort);
+        File.Exists(Path.Combine(_temporaryDirectory, ".workspace", "port.txt")).Should().BeTrue();
+    }
+
+    [Fact]
+    public void LoadFrom_WhenPortFileMissingAndGitIsDirectory_ShouldPickDefaultBasePort()
+    {
+        // Arrange: a normal repository root has `.git` as a DIRECTORY
+        Directory.CreateDirectory(Path.Combine(_temporaryDirectory, ".git"));
+
+        // Act
+        var allocation = PortAllocation.LoadFrom(_temporaryDirectory);
+
+        // Assert
+        allocation.BasePort.Should().Be(DefaultBasePort);
+        File.Exists(Path.Combine(_temporaryDirectory, ".workspace", "port.txt")).Should().BeTrue();
+    }
+}