unit test for postgres transaction

tests/unit/framework/db/pgsql/PostgreSQLConnectionTest.php

 <?php
 namespace yiiunit\framework\db\pgsql;
 
+use yii\db\Transaction;
 use yiiunit\framework\db\ConnectionTest;
 
 /**
@@ -48,4 +49,29 @@ class PostgreSQLConnectionTest extends ConnectionTest
         $this->assertEquals('{{column}}', $connection->quoteColumnName('{{column}}'));
         $this->assertEquals('(column)', $connection->quoteColumnName('(column)'));
     }
+
+	public function testTransactionIsolation()
+	{
+		$connection = $this->getConnection(true);
+
+		$transaction = $connection->beginTransaction();
+		$transaction->setIsolationLevel(Transaction::READ_UNCOMMITTED);
+		$transaction->commit();
+
+		$transaction = $connection->beginTransaction();
+		$transaction->setIsolationLevel(Transaction::READ_COMMITTED);
+		$transaction->commit();
+
+		$transaction = $connection->beginTransaction();
+		$transaction->setIsolationLevel(Transaction::REPEATABLE_READ);
+		$transaction->commit();
+
+		$transaction = $connection->beginTransaction();
+		$transaction->setIsolationLevel(Transaction::SERIALIZABLE);
+		$transaction->commit();
+
+		$transaction = $connection->beginTransaction();
+		$transaction->setIsolationLevel(Transaction::SERIALIZABLE . ' READ ONLY DEFERABLE');
+		$transaction->commit();
+	}
 }