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Fix Test-Connection to correctly report BufferSize of 0#27657

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raman118:fix/test-connection-buffersize-zero
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Fix Test-Connection to correctly report BufferSize of 0#27657
raman118 wants to merge 1 commit into
PowerShell:masterfrom
raman118:fix/test-connection-buffersize-zero

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@raman118 raman118 commented Jul 5, 2026

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Summary

This PR fixes a bug in Test-Connection where specifying -BufferSize 0 incorrectly reports a buffer size of 32 in the output object and the CLI
formatting tables, even though a 0-byte payload was actually sent.

What was broken & Root Cause

Previously, when creating the output PingStatus objects (both for standard pings and traceroutes), the cmdlet calculated the reported buffer size using this expression:
```csharp
buffer.Length == 0 ? DefaultSendBufferSize : buffer.Length

This logic was added in the past to support non-Windows platforms (like Linux/macOS), where Test-Connection sends a 0-length buffer under the hood
when using the default size of 32 (to run without requiring administrative/root privileges).

However, checking buffer.Length == 0 meant the code couldn't distinguish between:

  1. The default 32-byte size (which is sent as 0-length under the hood).
  2. An explicit user request for a 0-byte buffer size via -BufferSize 0 .

Because of this, both scenarios ended up reporting a buffer size of 32.

What changed

Instead of checking the underlying buffer.Length on the fly, we now pass the cmdlet's BufferSize property directly to the PingStatus constructor.

This works perfectly because:

• When using the default settings, BufferSize is 32 , so the output reports 32 .
• When the user specifies -BufferSize 0 , BufferSize is 0 , so the output correctly reports 0 .
• Any other custom buffer size is also reported exactly as requested.

How it was tested

  1. Added a new Pester test under test/powershell/Modules/Microsoft.PowerShell.Management/Test-Connection.Tests.ps1 to assert that -BufferSize 0 correctly returns a reported buffer size of 0 .
  2. Verified that the test fails on the old codebase and passes perfectly after applying the fix, alongside the other 26 tests in the test suite.

Fixes #27656

Use the requested BufferSize parameter value rather than the sent buffer length when constructing PingStatus objects. This prevents an empty buffer (sent when using -BufferSize 0 or the default) from always being reported as 32.
@raman118 raman118 requested a review from a team as a code owner July 5, 2026 03:51
Copilot AI review requested due to automatic review settings July 5, 2026 03:51
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Pull request overview

Fixes Test-Connection output reporting so that an explicitly requested -BufferSize 0 is reported as 0 (instead of being coerced to the default 32), aligning the PingStatus.BufferSize property and the default formatting table with the user’s requested value.

Changes:

  • Update TestConnectionCommand to pass the cmdlet’s BufferSize parameter value into PingStatus (instead of inferring from the underlying send buffer length).
  • Add a Pester regression test validating that -BufferSize 0 returns BufferSize = 0.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File Description
test/powershell/Modules/Microsoft.PowerShell.Management/Test-Connection.Tests.ps1 Adds regression coverage for -BufferSize 0 reporting.
src/Microsoft.PowerShell.Commands.Management/commands/management/TestConnectionCommand.cs Changes PingStatus construction to report the requested BufferSize value.

Comment on lines +488 to +489
// If we use the empty buffer for default size, we want to show
// the requested BufferSize (32) instead of the actual buffer length (0).
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Test-Connection -BufferSize 0 reports buffer size of 32

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