Created first common elements for functional tests

module/Common/test-func/DbUnit/DatabaseTestCase.php

@@ -0,0 +1,58 @@
+<?php
+declare(strict_types=1);
+
+namespace ShlinkioTest\Shlink\Common\DbUnit;
+
+use Doctrine\DBAL\Driver\PDOConnection;
+use Doctrine\ORM\EntityManagerInterface;
+use PHPUnit\DbUnit\Database\Connection as DbConn;
+use PHPUnit\DbUnit\DataSet\IDataSet as DataSet;
+use PHPUnit\DbUnit\TestCase;
+
+abstract class DatabaseTestCase extends TestCase
+{
+    const ENTITIES_TO_EMPTY = [];
+
+    /**
+     * @var EntityManagerInterface
+     */
+    public static $em;
+    /**
+     * @var DbConn
+     */
+    private static $conn;
+
+    public function getConnection(): DbConn
+    {
+        if (isset(self::$conn)) {
+            return self::$conn;
+        }
+
+        /** @var PDOConnection $pdo */
+        $pdo = static::$em->getConnection()->getWrappedConnection();
+        return self::$conn = $this->createDefaultDBConnection($pdo, static::$em->getConnection()->getDatabase());
+    }
+
+    public function getDataSet(): DataSet
+    {
+        return $this->createArrayDataSet([]);
+    }
+
+    protected function getEntityManager(): EntityManagerInterface
+    {
+        return static::$em;
+    }
+
+    public function tearDown()
+    {
+        // Empty all entity tables defined by this test after each test
+        foreach (static::ENTITIES_TO_EMPTY as $entityClass) {
+            $qb = $this->getEntityManager()->createQueryBuilder();
+            $qb->delete($entityClass, 'x');
+            $qb->getQuery()->execute();
+        }
+
+        // Clear entity manager
+        $this->getEntityManager()->clear();
+    }
+}