Add a unit test to check for casting a IQueryFunction

Signed-off-by: Joas Schilling <coding@schilljs.com>

tests/lib/DB/QueryBuilder/ExpressionBuilderDBTest.php

@@ -22,6 +22,7 @@
 namespace Test\DB\QueryBuilder;
 
 use OC\DB\QueryBuilder\Literal;
+use OCP\DB\QueryBuilder\IQueryBuilder;
 use Test\TestCase;
 
 /**
@@ -109,4 +110,37 @@ class ExpressionBuilderDBTest extends TestCase {
 		$result->closeCursor();
 		$this->assertEquals($match, $column);
 	}
+
+	public function testCastColumn(): void {
+		$appId = $this->getUniqueID('testing');
+		$this->createConfig($appId, '1', '4');
+
+		$query = $this->connection->getQueryBuilder();
+		$query->update('appconfig')
+			->set('configvalue',
+				$query->expr()->castColumn(
+					$query->createFunction(
+						'(' . $query->expr()->castColumn('configvalue', IQueryBuilder::PARAM_INT)
+						. ' + 1)'
+					)
+					, IQueryBuilder::PARAM_STR
+				)
+			)
+			->where($query->expr()->eq('appid', $query->createNamedParameter($appId)))
+			->andWhere($query->expr()->eq('configkey', $query->createNamedParameter('1')));
+
+		$result = $query->executeStatement();
+		$this->assertEquals(1, $result);
+	}
+
+	protected function createConfig($appId, $key, $value) {
+		$query = $this->connection->getQueryBuilder();
+		$query->insert('appconfig')
+			->values([
+				'appid' => $query->createNamedParameter($appId),
+				'configkey' => $query->createNamedParameter((string) $key),
+				'configvalue' => $query->createNamedParameter((string) $value),
+			])
+			->execute();
+	}
 }