silverstripe-postgresql/tests/PostgreSQLDatabaseTest.php

<?php
/**
 * @package postgresql
 * @subpackage tests
 */
class PostgreSQLDatabaseTest extends SapphireTest {
	function testReadOnlyTransaction(){

		if(
			DB::get_conn()->supportsTransactions() == true
			&& DB::get_conn() instanceof PostgreSQLDatabase
		){

			$page=new Page();
			$page->Title='Read only success';
			$page->write();

			DB::get_conn()->transactionStart('READ ONLY');

			try {
				$page=new Page();
				$page->Title='Read only page failed';
				$page->write();
			} catch (Exception $e) {
				//could not write this record
				//We need to do a rollback or a commit otherwise we'll get error messages
				DB::get_conn()->transactionRollback();
			}

			DB::get_conn()->transactionEnd();

			DataObject::flush_and_destroy_cache();

			$success=DataObject::get('Page', "\"Title\"='Read only success'");
			$fail=DataObject::get('Page', "\"Title\"='Read only page failed'");

			//This page should be in the system
			$this->assertTrue(is_object($success) && $success->exists());

			//This page should NOT exist, we had 'read only' permissions
			$this->assertFalse(is_object($fail) && $fail->exists());

		} else {
			$this->markTestSkipped('Current database is not PostgreSQL');
		}

	}
}