code: protected function createConfigurationDefinition()
      {
          $values = [
              'array_key_exists',
              'empty',
              'file_exists',
              'is_array',
              'is_bool',
              'is_callable',
              'is_double',
              'is_float',
              'is_infinite',
              'is_int',
              'is_integer',
              'is_long',
              'is_nan',
              'is_null',
              'is_numeric',
              'is_object',
              'is_real',
              'is_resource',
              'is_scalar',
              'is_string',
          ];
  
          sort($values);
  
          return new FixerConfigurationResolverRootless('functions', [
              (new FixerOptionBuilder('functions', 'List of assertions to fix (overrides `target`).'))
                  ->setAllowedTypes(['null', 'array'])
                  ->setAllowedValues([
                      null,
                      new AllowedValueSubset($values),
                  ])
                  ->setDefault(null)
                  ->setDeprecationMessage('Use option `target` instead.')
                  ->getOption(),
              (new FixerOptionBuilder('target', 'Target version of PHPUnit.'))
                  ->setAllowedTypes(['string'])
                  ->setAllowedValues([
                      PhpUnitTargetVersion::VERSION_3_0,
                      PhpUnitTargetVersion::VERSION_3_5,
                      PhpUnitTargetVersion::VERSION_5_0,
                      PhpUnitTargetVersion::VERSION_5_6,
                      PhpUnitTargetVersion::VERSION_NEWEST,
                  ])
                  ->setDefault(PhpUnitTargetVersion::VERSION_5_0) // @TODO 3.x: change to `VERSION_NEWEST`
                  ->getOption(),
          ], $this->getName());
      }
docs: {@inheritdoc}