chore: import upstream snapshot with attribution

dotnet/tests/Microsoft.Agents.AI.Tools.Shell.UnitTests/ShellResultTests.cs

@@ -0,0 +1,71 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+
+namespace Microsoft.Agents.AI.Tools.Shell.UnitTests;
+
+/// <summary>
+/// Branch coverage for <see cref="ShellResult.FormatForModel"/>. The output of
+/// this method is what the language model sees, so regressions directly
+/// affect agent behavior.
+/// </summary>
+public sealed class ShellResultTests
+{
+    [Fact]
+    public void FormatForModel_Success_IncludesStdoutAndExitCode()
+    {
+        var r = new ShellResult("hello\n", string.Empty, 0, TimeSpan.FromMilliseconds(5));
+        var s = r.FormatForModel();
+        Assert.Contains("hello", s, StringComparison.Ordinal);
+        Assert.Contains("exit_code: 0", s, StringComparison.Ordinal);
+        Assert.DoesNotContain("stderr:", s, StringComparison.Ordinal);
+        Assert.DoesNotContain("[stdout truncated]", s, StringComparison.Ordinal);
+        Assert.DoesNotContain("[command timed out]", s, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void FormatForModel_EmptyStdout_OmitsStdoutBlock()
+    {
+        var r = new ShellResult(string.Empty, string.Empty, 0, TimeSpan.Zero);
+        var s = r.FormatForModel();
+        // No stdout block, no stderr block — just the exit code line.
+        Assert.Equal("exit_code: 0", s);
+    }
+
+    [Fact]
+    public void FormatForModel_NonEmptyStderr_IncludesStderrLabel()
+    {
+        var r = new ShellResult(string.Empty, "boom\n", 1, TimeSpan.Zero);
+        var s = r.FormatForModel();
+        Assert.Contains("stderr: boom", s, StringComparison.Ordinal);
+        Assert.Contains("exit_code: 1", s, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void FormatForModel_Truncated_AppendsTruncatedMarker()
+    {
+        var r = new ShellResult("partial-output", string.Empty, 0, TimeSpan.Zero, Truncated: true);
+        var s = r.FormatForModel();
+        Assert.Contains("[stdout truncated]", s, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void FormatForModel_TimedOut_AppendsTimedOutMarker()
+    {
+        var r = new ShellResult(string.Empty, string.Empty, 124, TimeSpan.FromSeconds(30), TimedOut: true);
+        var s = r.FormatForModel();
+        Assert.Contains("[command timed out]", s, StringComparison.Ordinal);
+        Assert.Contains("exit_code: 124", s, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void FormatForModel_TruncatedButEmptyStdout_DoesNotEmitMarker()
+    {
+        // Marker is only emitted inside the stdout block; with empty stdout
+        // there's no block to attach it to.
+        var r = new ShellResult(string.Empty, "err\n", 1, TimeSpan.Zero, Truncated: true);
+        var s = r.FormatForModel();
+        Assert.DoesNotContain("[stdout truncated]", s, StringComparison.Ordinal);
+        Assert.Contains("stderr: err", s, StringComparison.Ordinal);
+    }
+}