diff --git a/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php b/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php
index 3d236f4869..869688b6fb 100644
--- a/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php
+++ b/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php
@@ -51,7 +51,6 @@ class TestSiteInstallCommand extends Command {
    */
   protected $databasePrefix;
 
-
   /**
    * The language to install the site in.
    *
@@ -71,7 +70,10 @@ protected function configure() {
       ->addOption('base_url', NULL, InputOption::VALUE_OPTIONAL, 'Base URL for site under test or SIMPLETEST_BASE_URL', getenv('SIMPLETEST_BASE_URL'))
       ->addOption('install_profile', NULL, InputOption::VALUE_OPTIONAL, 'Install profile to install the site in. Defaults to testing', 'testing')
       ->addOption('langcode', NULL, InputOption::VALUE_OPTIONAL, 'The language to install the site in. Defaults to en', 'en')
-      ->addOption('json', NULL, InputOption::VALUE_NONE, 'Output test site connection details in JSON');
+      ->addOption('json', NULL, InputOption::VALUE_NONE, 'Output test site connection details in JSON')
+      ->addUsage('--setup_class "\Drupal\TestSite\TestSiteInstallTestScript" --json')
+      ->addUsage('--install_profile demo_umami --langcode fr')
+      ->addUsage('--base_url "http://example.com" --db_url "mysql://username:password@localhost/databasename#table_prefix"');
   }
 
   /**
diff --git a/core/tests/Drupal/TestSite/Commands/TestSiteTearDownCommand.php b/core/tests/Drupal/TestSite/Commands/TestSiteTearDownCommand.php
index 4a6191f7d6..5b8fbba094 100644
--- a/core/tests/Drupal/TestSite/Commands/TestSiteTearDownCommand.php
+++ b/core/tests/Drupal/TestSite/Commands/TestSiteTearDownCommand.php
@@ -11,6 +11,7 @@
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Style\SymfonyStyle;
 use Symfony\Component\HttpFoundation\Request;
 
 /**
@@ -51,31 +52,42 @@ protected function configure() {
       ->setHelp('All the database tables and files will be removed.')
       ->addArgument('db_prefix', InputArgument::REQUIRED, 'The database prefix for the test site')
       ->addOption('db_url', NULL, InputOption::VALUE_OPTIONAL, 'URL for database or SIMPLETEST_DB', getenv('SIMPLETEST_DB'))
-      ->addOption('base_url', NULL, InputOption::VALUE_OPTIONAL, 'Base URL for site under test or SIMPLETEST_BASE_URL', getenv('SIMPLETEST_BASE_URL'));
+      ->addUsage('test12345678')
+      ->addUsage('test12345678 --db_url "mysql://username:password@localhost/databasename#table_prefix"');
   }
 
   /**
    * {@inheritdoc}
    */
   protected function execute(InputInterface $input, OutputInterface $output) {
-    $db_url = $input->getOption('db_url');
     $db_prefix = $input->getArgument('db_prefix');
-    $base_url = $input->getOption('base_url');
+    // Validate the db_prefix argument.
+    try {
+      $test_database = new TestDatabase($db_prefix);
+    }
+    catch (\InvalidArgumentException $e) {
+      $io = new SymfonyStyle($input, $output);
+      $io->getErrorStyle()->error("Invalid database prefix: $db_prefix\n\nValid database prefixes match the regular expression '/test(\d+)$/'. For example, 'test12345678'.");
+      // Display the synopsis of the command like Composer does.
+      $output->writeln(sprintf('<info>%s</info>', sprintf($this->getSynopsis(), $this->getName())), OutputInterface::VERBOSITY_QUIET);
+      return 1;
+    }
+
+    $db_url = $input->getOption('db_url');
     putenv("SIMPLETEST_DB=$db_url");
-    putenv("SIMPLETEST_BASE_URL=$base_url");
 
     $kernel = $this->bootstrapDrupal();
 
     // Handle the cleanup of the test site.
-    $this->tearDown($db_prefix, $db_url, $kernel->getAppRoot());
+    $this->tearDown($test_database, $db_url, $kernel->getAppRoot());
     $output->writeln("<info>Successfully uninstalled $db_prefix test site</info>");
   }
 
   /**
    * Removes a given instance by deleting all the database tables and files.
    *
-   * @param string $db_prefix
-   *   The used database prefix.
+   * @param \Drupal\Core\Test\TestDatabase $test_database
+   *   The test database object.
    * @param string $db_url
    *   The database URL.
    * @param string $app_root
@@ -83,10 +95,10 @@ protected function execute(InputInterface $input, OutputInterface $output) {
    *
    * @see \Drupal\Tests\BrowserTestBase::cleanupEnvironment()
    */
-  protected function tearDown($db_prefix, $db_url, $app_root) {
+  protected function tearDown(TestDatabase $test_database, $db_url, $app_root) {
     // Connect to the test database.
     $database = Database::convertDbUrlToConnectionInfo($db_url, $app_root);
-    $database['prefix'] = ['default' => $db_prefix];
+    $database['prefix'] = ['default' => $test_database->getDatabasePrefix()];
     Database::addConnectionInfo(__CLASS__, 'default', $database);
 
     // Remove all the tables.
@@ -94,7 +106,6 @@ protected function tearDown($db_prefix, $db_url, $app_root) {
     array_walk($schema->findTables('%'), [$schema, 'dropTable']);
 
     // Delete test site directory.
-    $test_database = new TestDatabase($db_prefix);
     file_unmanaged_delete_recursive($test_database->getTestSitePath(), [BrowserTestBase::class, 'filePreDeleteCallback']);
   }
 
diff --git a/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php b/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php
index b93e9d5f32..4f764df60b 100644
--- a/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php
+++ b/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php
@@ -195,6 +195,21 @@ public function testInstallInDifferentLanguage() {
     $this->assertCount(0, Database::getConnection('default', $this->addTestDatabase($db_prefix))->schema()->findTables('%'));
   }
 
+  /**
+   * @coversNothing
+   */
+  public function testTearDownDbPrefixValidation() {
+    $php_binary_finder = new PhpExecutableFinder();
+    $php_binary_path = $php_binary_finder->find();
+
+    $command_line = $php_binary_path . ' core/scripts/test-site.php tear-down not-a-valid-prefix';
+    $process = new Process($command_line, $this->root);
+    $process->setTimeout(500);
+    $process->run();
+    $this->assertSame(1, $process->getExitCode());
+    $this->assertContains('Invalid database prefix: not-a-valid-prefix', $process->getErrorOutput());
+  }
+
   /**
    * Adds the installed test site to the database connection info.
    *