diff --git a/tests/Doctrine/Functions/AbstractDoctrineFunctionTestCase.php b/tests/Doctrine/Functions/AbstractDoctrineFunctionTestCase.php
new file mode 100644
index 00000000..7bc3d628
--- /dev/null
+++ b/tests/Doctrine/Functions/AbstractDoctrineFunctionTestCase.php
@@ -0,0 +1,68 @@
+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2026 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace App\Tests\Doctrine\Functions;
+
+use Doctrine\DBAL\Connection;
+use Doctrine\DBAL\Platforms\AbstractPlatform;
+use Doctrine\ORM\Query\AST\Node;
+use Doctrine\ORM\Query\SqlWalker;
+use PHPUnit\Framework\TestCase;
+
+abstract class AbstractDoctrineFunctionTestCase extends TestCase
+{
+    protected function createSqlWalker(AbstractPlatform $platform, string $serverVersion = '11.0.0-MariaDB'): SqlWalker
+    {
+        $connection = $this->createMock(Connection::class);
+        $connection->method('getDatabasePlatform')->willReturn($platform);
+        $connection->method('getServerVersion')->willReturn($serverVersion);
+
+        $sqlWalker = $this->getMockBuilder(SqlWalker::class)
+            ->disableOriginalConstructor()
+            ->onlyMethods(['getConnection'])
+            ->getMock();
+
+        $sqlWalker->method('getConnection')->willReturn($connection);
+
+        return $sqlWalker;
+    }
+
+    protected function createNode(string $sql): Node
+    {
+        $node = $this->createMock(Node::class);
+        $node->method('dispatch')->willReturn($sql);
+
+        return $node;
+    }
+
+    protected function setObjectProperty(object $object, string $property, mixed $value): void
+    {
+        $reflection = new \ReflectionProperty($object, $property);
+        $reflection->setValue($object, $value);
+    }
+
+    protected function setStaticProperty(string $class, string $property, mixed $value): void
+    {
+        $reflection = new \ReflectionProperty($class, $property);
+        $reflection->setValue(null, $value);
+    }
+}
diff --git a/tests/Doctrine/Functions/ArrayPositionTest.php b/tests/Doctrine/Functions/ArrayPositionTest.php
new file mode 100644
index 00000000..7fdff42d
--- /dev/null
+++ b/tests/Doctrine/Functions/ArrayPositionTest.php
@@ -0,0 +1,42 @@
+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2026 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+
+namespace App\Tests\Doctrine\Functions;
+
+use App\Doctrine\Functions\ArrayPosition;
+use Doctrine\DBAL\Platforms\PostgreSQLPlatform;
+
+final class ArrayPositionTest extends AbstractDoctrineFunctionTestCase
+{
+    public function testArrayPositionBuildsSql(): void
+    {
+        $function = new ArrayPosition('ARRAY_POSITION');
+        $this->setObjectProperty($function, 'array', $this->createNode(':ids'));
+        $this->setObjectProperty($function, 'field', $this->createNode('p.id'));
+
+        $sql = $function->getSql($this->createSqlWalker(new PostgreSQLPlatform()));
+
+        $this->assertSame('ARRAY_POSITION(:ids, p.id)', $sql);
+    }
+}
+
diff --git a/tests/Doctrine/Functions/Field2Test.php b/tests/Doctrine/Functions/Field2Test.php
new file mode 100644
index 00000000..d25e511f
--- /dev/null
+++ b/tests/Doctrine/Functions/Field2Test.php
@@ -0,0 +1,45 @@
+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2026 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace App\Tests\Doctrine\Functions;
+
+use App\Doctrine\Functions\Field2;
+use Doctrine\DBAL\Platforms\MySQLPlatform;
+
+final class Field2Test extends AbstractDoctrineFunctionTestCase
+{
+    public function testField2BuildsSql(): void
+    {
+        $function = new Field2('FIELD2');
+        $this->setObjectProperty($function, 'field', $this->createNode('p.id'));
+        $this->setObjectProperty($function, 'values', [
+            $this->createNode('1'),
+            $this->createNode('2'),
+            $this->createNode('3'),
+        ]);
+
+        $sql = $function->getSql($this->createSqlWalker(new MySQLPlatform()));
+
+        $this->assertSame('FIELD2(p.id, 1, 2, 3)', $sql);
+    }
+}
+
diff --git a/tests/Doctrine/Functions/ILikeTest.php b/tests/Doctrine/Functions/ILikeTest.php
new file mode 100644
index 00000000..4541e9c9
--- /dev/null
+++ b/tests/Doctrine/Functions/ILikeTest.php
@@ -0,0 +1,66 @@
+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2026 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace App\Tests\Doctrine\Functions;
+
+use App\Doctrine\Functions\ILike;
+use Doctrine\DBAL\Platforms\AbstractPlatform;
+use Doctrine\DBAL\Platforms\MySQLPlatform;
+use Doctrine\DBAL\Platforms\PostgreSQLPlatform;
+use Doctrine\DBAL\Platforms\SQLitePlatform;
+use Doctrine\DBAL\Platforms\SQLServerPlatform;
+use PHPUnit\Framework\Attributes\DataProvider;
+
+final class ILikeTest extends AbstractDoctrineFunctionTestCase
+{
+    public static function iLikePlatformProvider(): \Generator
+    {
+        yield 'mysql' => [new MySQLPlatform(), '(part_name LIKE :pattern)'];
+        yield 'postgres' => [new PostgreSQLPlatform(), '(part_name ILIKE :pattern)'];
+        yield 'sqlite' => [new SQLitePlatform(), "(part_name LIKE :pattern ESCAPE '\\')"];
+    }
+
+    #[DataProvider('iLikePlatformProvider')]
+    public function testILikeUsesExpectedOperator(AbstractPlatform $platform, string $expectedSql): void
+    {
+        $function = new ILike('ILIKE');
+        $function->value = $this->createNode('part_name');
+        $function->expr = $this->createNode(':pattern');
+
+        $sql = $function->getSql($this->createSqlWalker($platform));
+
+        $this->assertSame($expectedSql, $sql);
+    }
+
+    public function testILikeThrowsOnUnsupportedPlatform(): void
+    {
+        $function = new ILike('ILIKE');
+        $function->value = $this->createNode('part_name');
+        $function->expr = $this->createNode(':pattern');
+
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage('does not support case insensitive like expressions');
+
+        $function->getSql($this->createSqlWalker(new SQLServerPlatform()));
+    }
+}
+
diff --git a/tests/Doctrine/Functions/NatsortTest.php b/tests/Doctrine/Functions/NatsortTest.php
new file mode 100644
index 00000000..fd10199f
--- /dev/null
+++ b/tests/Doctrine/Functions/NatsortTest.php
@@ -0,0 +1,95 @@
+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2026 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace App\Tests\Doctrine\Functions;
+
+use App\Doctrine\Functions\Natsort;
+use Doctrine\DBAL\Platforms\MariaDBPlatform;
+use Doctrine\DBAL\Platforms\MySQLPlatform;
+use Doctrine\DBAL\Platforms\PostgreSQLPlatform;
+use Doctrine\DBAL\Platforms\SQLitePlatform;
+
+final class NatsortTest extends AbstractDoctrineFunctionTestCase
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        Natsort::allowSlowNaturalSort(false);
+        $this->setStaticProperty(Natsort::class, 'supportsNaturalSort', null);
+    }
+
+    public function testNatsortUsesPostgresCollation(): void
+    {
+        $function = new Natsort('NATSORT');
+        $this->setObjectProperty($function, 'field', $this->createNode('part_name'));
+
+        $sql = $function->getSql($this->createSqlWalker(new PostgreSQLPlatform()));
+
+        $this->assertSame('part_name COLLATE numeric', $sql);
+    }
+
+    public function testNatsortUsesMariaDbNativeFunctionOnSupportedVersion(): void
+    {
+        $function = new Natsort('NATSORT');
+        $this->setObjectProperty($function, 'field', $this->createNode('part_name'));
+
+        $sql = $function->getSql($this->createSqlWalker(new MariaDBPlatform(), '10.11.2-MariaDB'));
+
+        $this->assertSame('NATURAL_SORT_KEY(part_name)', $sql);
+    }
+
+    public function testNatsortFallsBackWithoutSlowSort(): void
+    {
+        $function = new Natsort('NATSORT');
+        $this->setObjectProperty($function, 'field', $this->createNode('part_name'));
+
+        $sql = $function->getSql($this->createSqlWalker(new MariaDBPlatform(), '10.6.10-MariaDB'));
+
+        $this->assertSame('part_name', $sql);
+    }
+
+    public function testNatsortUsesSlowSortFunctionOnMySqlWhenEnabled(): void
+    {
+        Natsort::allowSlowNaturalSort();
+
+        $function = new Natsort('NATSORT');
+        $this->setObjectProperty($function, 'field', $this->createNode('part_name'));
+
+        $sql = $function->getSql($this->createSqlWalker(new MySQLPlatform()));
+
+        $this->assertSame('NatSortKey(part_name, 0)', $sql);
+    }
+
+    public function testNatsortUsesSlowSortCollationOnSqliteWhenEnabled(): void
+    {
+        Natsort::allowSlowNaturalSort();
+
+        $function = new Natsort('NATSORT');
+        $this->setObjectProperty($function, 'field', $this->createNode('part_name'));
+
+        $sql = $function->getSql($this->createSqlWalker(new SQLitePlatform()));
+
+        $this->assertSame('part_name COLLATE NATURAL_CMP', $sql);
+    }
+}
+
diff --git a/tests/Doctrine/Functions/RegexpTest.php b/tests/Doctrine/Functions/RegexpTest.php
new file mode 100644
index 00000000..d1866210
--- /dev/null
+++ b/tests/Doctrine/Functions/RegexpTest.php
@@ -0,0 +1,66 @@
+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2026 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace App\Tests\Doctrine\Functions;
+
+use App\Doctrine\Functions\Regexp;
+use Doctrine\DBAL\Platforms\AbstractPlatform;
+use Doctrine\DBAL\Platforms\MySQLPlatform;
+use Doctrine\DBAL\Platforms\PostgreSQLPlatform;
+use Doctrine\DBAL\Platforms\SQLitePlatform;
+use Doctrine\DBAL\Platforms\SQLServerPlatform;
+use PHPUnit\Framework\Attributes\DataProvider;
+
+final class RegexpTest extends AbstractDoctrineFunctionTestCase
+{
+    public static function regexpPlatformProvider(): \Generator
+    {
+        yield 'mysql' => [new MySQLPlatform(), '(part_name REGEXP :regex)'];
+        yield 'sqlite' => [new SQLitePlatform(), '(part_name REGEXP :regex)'];
+        yield 'postgres' => [new PostgreSQLPlatform(), '(part_name ~* :regex)'];
+    }
+
+    #[DataProvider('regexpPlatformProvider')]
+    public function testRegexpUsesExpectedOperator(AbstractPlatform $platform, string $expectedSql): void
+    {
+        $function = new Regexp('REGEXP');
+        $this->setObjectProperty($function, 'value', $this->createNode('part_name'));
+        $this->setObjectProperty($function, 'regexp', $this->createNode(':regex'));
+
+        $sql = $function->getSql($this->createSqlWalker($platform));
+
+        $this->assertSame($expectedSql, $sql);
+    }
+
+    public function testRegexpThrowsOnUnsupportedPlatform(): void
+    {
+        $function = new Regexp('REGEXP');
+        $this->setObjectProperty($function, 'value', $this->createNode('part_name'));
+        $this->setObjectProperty($function, 'regexp', $this->createNode(':regex'));
+
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage('does not support regular expressions');
+
+        $function->getSql($this->createSqlWalker(new SQLServerPlatform()));
+    }
+}
+