test(db): cover distinct uid fetch compatibility

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

tests/php/Unit/Db/FieldValueMapperTest.php

@@ -0,0 +1,67 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2026 LibreCode coop and LibreCode contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+declare(strict_types=1);
+
+namespace OCA\ProfileFields\Tests\Unit\Db;
+
+use OCA\ProfileFields\Db\FieldValueMapper;
+use OCP\DB\IResult;
+use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\IDBConnection;
+use PDO;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+
+class FieldValueMapperTest extends TestCase {
+	private IDBConnection&MockObject $db;
+	private IQueryBuilder&MockObject $queryBuilder;
+	private IResult&MockObject $result;
+	private FieldValueMapper $mapper;
+
+	protected function setUp(): void {
+		parent::setUp();
+		$this->db = $this->createMock(IDBConnection::class);
+		$this->queryBuilder = $this->createMock(IQueryBuilder::class);
+		$this->result = $this->createMock(IResult::class);
+		$this->mapper = new FieldValueMapper($this->db);
+	}
+
+	public function testFindDistinctUserUidsUsesFetchAllColumnModeForCompatibility(): void {
+		$this->db->expects($this->once())
+			->method('getQueryBuilder')
+			->willReturn($this->queryBuilder);
+
+		$this->queryBuilder->expects($this->once())
+			->method('selectDistinct')
+			->with('user_uid')
+			->willReturnSelf();
+		$this->queryBuilder->expects($this->once())
+			->method('from')
+			->with('profile_fields_values')
+			->willReturnSelf();
+		$this->queryBuilder->expects($this->once())
+			->method('orderBy')
+			->with('user_uid', 'ASC')
+			->willReturnSelf();
+		$this->queryBuilder->expects($this->once())
+			->method('executeQuery')
+			->willReturn($this->result);
+
+		$this->result->expects($this->once())
+			->method('fetchAll')
+			->with(PDO::FETCH_COLUMN)
+			->willReturn(['alice', 7, 'bob']);
+		$this->result->expects($this->never())
+			->method('fetchFirstColumn');
+		$this->result->expects($this->once())
+			->method('closeCursor')
+			->willReturn(true);
+
+		$this->assertSame(['alice', '7', 'bob'], $this->mapper->findDistinctUserUids());
+	}
+}