diff -u b/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
--- b/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -9,6 +9,7 @@
 use Drupal\Component\Utility\Html;
 use Drupal\Component\Utility\Timer;
 use Drupal\Component\Uuid\Php;
+use Drupal\Core\Composer\Composer;
 use Drupal\Core\Database\Database;
 use Drupal\Core\Site\Settings;
 use Drupal\Core\StreamWrapper\PublicStream;
@@ -137,7 +138,7 @@
 else {
   $phpunit_version = Version::id();
 }
-if (version_compare(PHP_MAJOR_VERSION . '.' . PHP_MINOR_VERSION, '7.2') >= 0 && version_compare($phpunit_version, '6.1') < 0) {
+if (!Composer::upgradePHPUnitCheck($phpunit_version)) {
   simpletest_script_print_error("PHPUnit testing framework version 6 or greater is required when running on PHP 7.2 or greater. Run the command 'composer run-script drupal-phpunit-upgrade' in order to fix this.");
   exit(SIMPLETEST_SCRIPT_EXIT_FAILURE);
 }
@@ -465,10 +466,8 @@
 
   // Detect if we're in the top-level process using the private 'execute-test'
   // argument. Determine if being run on drupal.org's testing infrastructure
-  // using the DCI_JobType environmental variable so we can update PHPUnit
-  // automatically. In all other cases if an update is necessary, an error
-  // message will be emitted telling the user to do the upgrade themselves.
-  if (!$args['execute-test'] && getenv('DCI_JobType') !== FALSE) {
+  // using the presence of 'drupaltestbot' in the database url.
+  if (!$args['execute-test'] && preg_match('/drupaltestbot/', $args['dburl'])) {
     // Update PHPUnit if needed and possible. There is a later check once the
     // autoloader is in place to ensure we're on the correct version. We need to
     // do this before the autoloader is in place to ensure that it is correct.
diff -u b/core/tests/bootstrap.php b/core/tests/bootstrap.php
--- b/core/tests/bootstrap.php
+++ b/core/tests/bootstrap.php
@@ -8,6 +8,7 @@
  */
 
 use Drupal\Component\Assertion\Handle;
+use Drupal\Core\Composer\Composer;
 use PHPUnit\Runner\Version;
 
 /**
@@ -157,7 +158,7 @@
 else {
   $phpunit_version = Version::id();
 }
-if (version_compare(PHP_MAJOR_VERSION . '.' . PHP_MINOR_VERSION, '7.2') >= 0 && version_compare($phpunit_version, '6.1') < 0) {
+if (!Composer::upgradePHPUnitCheck($phpunit_version)) {
   $message = "PHPUnit testing framework version 6 or greater is required when running on PHP 7.2 or greater. Run the command 'composer run-script drupal-phpunit-upgrade' in order to fix this.";
   echo "\033[31m" . $message . "\n\033[0m";
   exit(1);
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Composer/Composer.php
+++ b/core/lib/Drupal/Core/Composer/Composer.php
@@ -162,13 +162,29 @@ public static function upgradePHPUnit(Event $event) {
 
     // If the PHP version is 7.2 or above and PHPUnit is less than version 6
     // call the drupal-phpunit-upgrade script to upgrade PHPUnit.
-    if (version_compare(PHP_MAJOR_VERSION . '.' . PHP_MINOR_VERSION, '7.2') >= 0 && version_compare($phpunit_package->getVersion(), '6.1') < 0) {
+    if (!static::upgradePHPUnitCheck($phpunit_package->getVersion())) {
       $event->getComposer()
         ->getEventDispatcher()
         ->dispatchScript('drupal-phpunit-upgrade');
     }
   }
 
+  /**
+   * Determines if PHPUnit needs to be upgraded.
+   *
+   * This method is located in this file because it is possible that it is
+   * called before the autoloader is available.
+   *
+   * @param string $phpunit_version
+   *   The PHPUnit version string.
+   *
+   * @return bool
+   *   TRUE if the PHPUnit needs to be upgraded, FALSE if not.
+   */
+  public static function upgradePHPUnitCheck($phpunit_version) {
+    return !(version_compare(PHP_MAJOR_VERSION . '.' . PHP_MINOR_VERSION, '7.2') >= 0 && version_compare($phpunit_version, '6.1') < 0);
+  }
+
   /**
    * Remove possibly problematic test files from vendored projects.
    *