Fix Win32Exception when stopping Elastic Agent service in transient state during test cleanup

[Copilot]

Clean-ElasticAgentService called Stop-Service unconditionally, which throws Win32Exception: The service cannot accept control messages at this time when the service is in StartPending or StopPending. The exception propagated through Clean-ElasticAgent, skipping Clean-ElasticAgentProcess and Clean-ElasticAgentDirectory, leaving the binary on disk and failing the Check-AgentRemnants assertion.

Changes

• src/agent-qa/helpers.ps1 — Clean-ElasticAgentService
  • Wait up to 30 seconds for the service to reach a stable state (Running or Stopped) before attempting to stop it
  • Emit a Write-Warning if the timeout expires with the service still in a transient state
  • Wrap Stop-Service -Force in try/catch to log stop failures as warnings rather than propagating exceptions that abort the cleanup sequence
  • Skip Stop-Service entirely if the service is already Stopped

# Before: throws Win32Exception if service is StartPending/StopPending
Stop-Service 'Elastic Agent'

# After: waits for stable state, then stops gracefully
while ($service.Status -notin @('Running', 'Stopped') -and (Get-Date) -lt $timeout) {
    Start-Sleep -Seconds 1
    $service.Refresh()
}
if ($service.Status -ne 'Stopped') {
    try {
        Stop-Service 'Elastic Agent' -Force
    } catch {
        Write-Warning "Failed to stop 'Elastic Agent' service: $_"
    }
}

Original prompt

---

This section details on the original issue you should resolve

<issue_title>There are test failures</issue_title>
<issue_description>See https://buildkite.com/elastic/elastic-stack-installers/builds/13650 (changes are not related to the project itself but adding some file to enable some new CI capabilities)

2025-10-22 17:54:48 UTC | [-] Can be installed in Fleet mode and uninstalled via GUID in default mode 27ms (26ms\|1ms)
-- | --
  | 2025-10-22 17:54:48 UTC | [0] Win32Exception: The service cannot accept control messages at this time.
  | 2025-10-22 17:54:48 UTC | InvalidOperationException: Cannot stop 'Elastic Agent' service on computer '.'.
  | 2025-10-22 17:54:48 UTC | ServiceCommandException: Service 'Elastic Agent (Elastic Agent)' cannot be stopped due to the following error: Cannot stop 'Elastic Agent' service on computer '.'.
  | 2025-10-22 17:54:48 UTC | at Clean-ElasticAgentService, C:\buildkite-agent\builds\bk-agent-prod-gcp-1761153718403188678\elastic\elastic-stack-installers\src\agent-qa\helpers.ps1:338
  | 2025-10-22 17:54:48 UTC | at Clean-ElasticAgent, C:\buildkite-agent\builds\bk-agent-prod-gcp-1761153718403188678\elastic\elastic-stack-installers\src\agent-qa\helpers.ps1:320
  | 2025-10-22 17:54:48 UTC | at <ScriptBlock>, C:\buildkite-agent\builds\bk-agent-prod-gcp-1761153718403188678\elastic\elastic-stack-installers\src\agent-qa\msi.tests.ps1:99
  | 2025-10-22 17:54:48 UTC | [1] Expected $false, because The agent should have been cleaned up already, but got $true.
  | 2025-10-22 17:54:48 UTC | at Is-AgentBinaryPresent \| Should -BeFalse -Because "The agent should have been cleaned up already", C:\buildkite-agent\builds\bk-agent-prod-gcp-1761153718403188678\elastic\elastic-stack-installers\src\agent-qa\msi.tests.ps1:72
  | 2025-10-22 17:54:48 UTC | at Check-AgentRemnants, C:\buildkite-agent\builds\bk-agent-prod-gcp-1761153718403188678\elastic\elastic-stack-installers\src\agent-qa\msi.tests.ps1:72
  | 2025-10-22 17:54:48 UTC | at <ScriptBlock>, C:\buildkite-agent\builds\bk-agent-prod-gcp-1761153718403188678\elastic\elastic-stack-installers\src\agent-qa\msi.tests.ps1:109
  | 2025-10-22 17:54:48 UTC | Tests completed in 855.61s
  | 2025-10-22 17:54:48 UTC | Tests Passed: 4, Failed: 14, Skipped: 0, Inconclusive: 0, NotRun: 0
  | 2025-10-22 17:54:48 UTC | Exception: Pester run failed, because 14 tests failed
  | 2025-10-22 17:54:49 UTC | Child pwsh process returned 1, a non zero exit code
  | 2025-10-22 17:54:49 UTC | Testing Failed
  | 2025-10-22 17:54:49 UTC | C:\buildkite-agent\builds\bk-agent-prod-gcp-1761153718403188678\elastic\elastic-stack-installers\.buildkite\scripts\bui
  | 2025-10-22 17:54:49 UTC | ld.ps1 : Tests failed.
  | 2025-10-22 17:54:49 UTC | At line:1 char:1
  | 2025-10-22 17:54:49 UTC | + .\.buildkite\scripts\build.ps1
  | 2025-10-22 17:54:49 UTC | + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  | 2025-10-22 17:54:49 UTC | + CategoryInfo          : NotSpecified: (:) [Write-Error], WriteErrorException
  | 2025-10-22 17:54:49 UTC | + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,build.ps1
  | 2025-10-22 17:54:49 UTC |  
  | 2025-10-22 17:54:49 UTC | ���� Error: The command exited with status 1
  | 2025-10-22 17:54:49 UTC | user command error: exit status 1

Reproduction

Create a feature branch and its PR.

Then waitn for the CI to run
</issue_description>

<agent_instructions>Review the GH issue description and comments that contain all the ifnormation from the errors that are happening in the CI.

Try to reproduce the error loclaly and find what's causing the problem</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@v1v ```

 

Creating "C:\buildkite-agent\builds\bk-agent-prod-gcp-1773340373614086112\elastic\elastic-stack-installers"

cd C:\buildkite-agent\builds\bk-agent-prod-gcp-1773340373614086112\elastic\elastic-stack-installers

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• Fixes There are test failures #341

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[v1v]

buildkite test