PhpUnitCliTest fails outside of CI

Problem/Motivation

The problem is with this assertion.

    $this->assertStringContainsString('Drupal_Tests_image_Functional_ImageDimensionsTest-1', $process->getOutput());

Because the number attached to the test is based on files on the filesystem, if you've ever run a test its very unlikely to start with a one. and so the output will fail.

For example, my unit test suite run had this failure.

2) Drupal\Tests\Core\Test\PhpUnitCliTest::testFunctionalTestDebugHtmlOutput
Failed asserting that 'PHPUnit 9.5.20 #StandWithUkraine\n
\n
Runtime:       PHP 8.1.2\n
Configuration: /app/core/phpunit.xml.dist\n
\n
Testing Drupal\Tests\image\Functional\ImageDimensionsTest\n
.                                                                   1 / 1 (100%)\n
\n
Time: 00:07.274, Memory: 10.00 MB\n
\n
OK (1 test, 60 assertions)\n
\n
HTML output was generated\n
http://d10.lndo.site/sites/simpletest/browser_output/Drupal_Tests_image_Functional_ImageDimensionsTest-51-73418261.html\n
http://d10.lndo.site/sites/simpletest/browser_output/Drupal_Tests_image_Functional_ImageDimensionsTest-52-73418261.html\n
http://d10.lndo.site/sites/simpletest/browser_output/Drupal_Tests_image_Functional_ImageDimensionsTest-53-73418261.html\n
http://d10.lndo.site/sites/simpletest/browser_output/Drupal_Tests_image_Functional_ImageDimensionsTest-54-73418261.html\n
http://d10.lndo.site/sites/simpletest/browser_output/Drupal_Tests_image_Functional_ImageDimensionsTest-55-73418261.html\n
http://d10.lndo.site/sites/simpletest/browser_output/Drupal_Tests_image_Functional_ImageDimensionsTest-56-73418261.html\n
http://d10.lndo.site/sites/simpletest/browser_output/Drupal_Tests_image_Functional_ImageDimensionsTest-57-73418261.html\n
http://d10.lndo.site/sites/simpletest/browser_output/Drupal_Tests_image_Functional_ImageDimensionsTest-58-73418261.html\n
http://d10.lndo.site/sites/simpletest/browser_output/Drupal_Tests_image_Functional_ImageDimensionsTest-59-73418261.html\n
http://d10.lndo.site/sites/simpletest/browser_output/Drupal_Tests_image_Functional_ImageDimensionsTest-60-73418261.html\n
' contains "Drupal_Tests_image_Functional_ImageDimensionsTest-1".

Steps to reproduce

This is one of the sometimes frustrating unit tests that require more then unit tests to function. I only mention this because you'll need a test setup that can run functional tests to run this unit tests and recreate the failure. With the appropriate collection of environment variables though you can run this to recreate it.

php ./vendor/bin/phpunit -c core core/tests/Drupal/Tests/Core/Test/PhpUnitCliTest.php
php ./vendor/bin/phpunit -c core core/tests/Drupal/Tests/Core/Test/PhpUnitCliTest.php
php ./vendor/bin/phpunit -c core core/tests/Drupal/Tests/Core/Test/PhpUnitCliTest.php

The third run should create results outside the teens causing the failure.

Proposed resolution

Remove the -1 from the assertion? I'm not sure what the intention was but I don't think its needed.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet