Constructive description here

vendor/fzaninotto/faker/test/Faker/Provider/es_ES/PersonTest.php

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+<?php
+
+namespace Faker\Test\Provider\es_ES;
+
+use Faker\Generator;
+use Faker\Provider\es_ES\Person;
+
+class PersonTest extends \PHPUnit_Framework_TestCase
+{
+    public function setUp()
+    {
+        $faker = new Generator();
+        $faker->seed(1);
+        $faker->addProvider(new Person($faker));
+        $this->faker = $faker;
+    }
+
+    public function testDNI()
+    {
+        $dni = $this->faker->dni;
+        $this->assertTrue($this->isValidDNI($dni));
+    }
+
+    // validation taken from http://kiwwito.com/php-function-for-spanish-dni-nie-validation/
+    public function isValidDNI($string)
+    {
+        if (strlen($string) != 9 ||
+            preg_match('/^[XYZ]?([0-9]{7,8})([A-Z])$/i', $string, $matches) !== 1) {
+            return false;
+        }
+
+        $map = 'TRWAGMYFPDXBNJZSQVHLCKE';
+
+        list(, $number, $letter) = $matches;
+
+        return strtoupper($letter) === $map[((int) $number) % 23];
+    }
+}