Add test for CmdHelper to prevent stdout/stderr deadlock

framework/test/Volo.Abp.Cli.Core.Tests/Volo/Abp/Cli/Utils/CmdHelper_Tests.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+using Shouldly;
+using Volo.Abp.Cli.Utils;
+using Xunit;
+
+namespace Volo.Abp.Cli.Utils;
+
+public class CmdHelper_Tests : AbpCliTestBase
+{
+    private readonly ICmdHelper _cmdHelper;
+
+    public CmdHelper_Tests()
+    {
+        _cmdHelper = GetRequiredService<ICmdHelper>();
+    }
+
+    [Fact]
+    public async Task RunCmdAndGetOutput_Should_Not_Deadlock_With_Large_Stdout_And_Stderr()
+    {
+        // Reproduces the deadlock bug where sequential ReadToEnd() on stdout then stderr
+        // would block indefinitely when both pipe buffers (~64 KB on Linux/macOS, ~4 KB on
+        // Windows) filled up simultaneously. The process was blocked writing to stderr while
+        // the caller was blocked waiting for stdout to close — a classic pipe deadlock.
+        //
+        // The fix reads both streams concurrently via ReadToEndAsync + Task.WhenAll, which
+        // drains both pipes at the same time and avoids the deadlock.
+        var command = RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
+            ? @"for /L %i in (1,1,3000) do @(echo stdout-line-%i & echo stderr-line-%i 1>&2)"
+            : "for i in $(seq 1 5000); do echo stdout-line-$i; echo stderr-line-$i >&2; done";
+
+        string output = null;
+        var cmdTask = Task.Run(() => output = _cmdHelper.RunCmdAndGetOutput(command));
+        var completed = await Task.WhenAny(cmdTask, Task.Delay(TimeSpan.FromSeconds(30)));
+
+        // The original sequential code deadlocked here; 30 s is a generous upper bound.
+        (completed == cmdTask).ShouldBeTrue(
+            "RunCmdAndGetOutput should not deadlock when both stdout and stderr produce large output");
+
+        await cmdTask;
+
+        output.ShouldNotBeNullOrWhiteSpace();
+        output.ShouldContain("stdout-line-");
+        output.ShouldContain("stderr-line-");
+    }
+}