Add functional test for comit() returning false

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

@@ -0,0 +1,53 @@
+<?php
+
+namespace Doctrine\Tests\DBAL\Functional;
+
+use Doctrine\DBAL\Schema\Table;
+use Doctrine\Tests\DbalFunctionalTestCase;
+use Throwable;
+use function in_array;
+use function sleep;
+
+class TransactionTest extends DbalFunctionalTestCase
+{
+    protected function setUp() : void
+    {
+        parent::setUp();
+
+        if (in_array($this->connection->getDatabasePlatform()->getName(), ['mysql'])) {
+            return;
+        }
+
+        $this->markTestSkipped('Restricted to MySQL.');
+    }
+
+    protected function tearDown() : void
+    {
+        $this->resetSharedConn();
+
+        parent::tearDown();
+    }
+
+    public function testCommitFalse() : void
+    {
+        $this->connection->query('SET SESSION wait_timeout=1');
+
+        $table = new Table('foo');
+        $table->addColumn('id', 'integer');
+        $table->setPrimaryKey(['id']);
+
+        $this->connection->getSchemaManager()->createTable($table);
+
+        self::assertEquals('foo', $table->getName());
+        try {
+            $this->assertTrue($this->connection->beginTransaction());
+            $this->connection->executeUpdate('INSERT INTO foo (id) VALUES(1)');
+
+            sleep(2); // during the sleep mysql will close the connection
+
+            $this->assertFalse(@$this->connection->commit()); // we will ignore `MySQL server has gone away` warnings
+        } catch (Throwable $exception) {
+            $this->fail('Is the PHP/PDO bug https://bugs.php.net/bug.php?id=66528 fixed? Normally no exception is thrown.');
+        }
+    }
+}