chore: Improve device test output (#4997)

Author: jamescrosswell

scripts/device-test.ps1

@@ -93,16 +93,29 @@ try
             xharness $group test $arguments --output-directory=test_output
             if ($LASTEXITCODE -ne 0)
             {
+                $testResultsXml = './test_output/TestResults.xml'
+                if (Test-Path $testResultsXml)
+                {
+                    $failedTests = Select-String -Path $testResultsXml -Pattern 'result="Fail"'
+                    if ($failedTests)
+                    {
+                        Write-Host "`nFailed tests:"
+                        $failedTests | ForEach-Object { Write-Host $_.Line }
+                    }
+                }
                 throw 'xharness run failed with non-zero exit code'
             }
         }
         finally
         {
             if ($CI)
             {
-                scripts/parse-xunit2-xml.ps1 (Get-Item ./test_output/*.xml).FullName | Out-File $env:GITHUB_STEP_SUMMARY
+                $xmlFiles = Get-Item ./test_output/*.xml -ErrorAction SilentlyContinue
+                if ($xmlFiles)
+                {
+                    scripts/parse-xunit2-xml.ps1 $xmlFiles.FullName | Out-File $env:GITHUB_STEP_SUMMARY
+                }
             }
-
         }
     }
 }