Refactor PostgreSQL lastInsertId() test which fails on travis

tests/Doctrine/Tests/DBAL/Functional/WriteTest.php

@@ -153,16 +153,21 @@ class WriteTest extends \Doctrine\Tests\DbalFunctionalTestCase
             $this->markTestSkipped('Test only works on platforms with sequences.');
         }
 
-        $sequence = new \Doctrine\DBAL\Schema\Sequence('write_table_seq');
+        $sequence = new \Doctrine\DBAL\Schema\Sequence('write_table_id_seq');
         try {
-            $this->_conn->getSchemaManager()->dropSequence($sequence);
-        } catch(\Exception $e) {}
-        $this->_conn->getSchemaManager()->createSequence($sequence);
+            $this->_conn->getSchemaManager()->createSequence($sequence);
+        } catch(\Exception $e) {
+        }
+
+        $sequences = $this->_conn->getSchemaManager()->listSequences();
+        $this->assertEquals(1, count(array_filter($sequences, function($sequence) {
+            return $sequence->getName() === 'write_table_id_seq';
+        })));
 
-        $stmt = $this->_conn->query($this->_conn->getDatabasePlatform()->getSequenceNextValSQL('write_table_seq'));
+        $stmt = $this->_conn->query($this->_conn->getDatabasePlatform()->getSequenceNextValSQL('write_table_id_seq'));
         $nextSequenceVal = $stmt->fetchColumn();
 
-        $lastInsertId = $this->_conn->lastInsertId('write_table_seq');
+        $lastInsertId = $this->_conn->lastInsertId('write_table_id_seq');
 
         $this->assertTrue($lastInsertId > 0);
         $this->assertEquals($nextSequenceVal, $lastInsertId);