addTestDatabase example

$php_executable_finder = new PhpExecutableFinder();
    $this->php = $php_executable_finder->find();
    $this->root = dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__)), 2);
  }

  /** * @coversNothing */
  public function testInstallWithNonExistingFile() {

    // Create a connection to the DB configured in SIMPLETEST_DB.     $connection = Database::getConnection('default', $this->addTestDatabase(''));
    $table_count = count($connection->schema()->findTables('%'));

    $command_line = $this->php . ' core/scripts/test-site.php install --setup-file "this-class-does-not-exist" --db-url "' . getenv('SIMPLETEST_DB') . '"';
    $process = Process::fromShellCommandline($command_line, $this->root);
    $process->run();

    $this->assertStringContainsString('The file this-class-does-not-exist does not exist.', $process->getErrorOutput());
    $this->assertSame(1, $process->getExitCode());
    $this->assertCount($table_count, $connection->schema()->findTables('%'), 'No additional tables created in the database');
  }