broken test

<?php
/* Run with PHPUnit 3.7.38 by Sebastian Bergmann
 * Silverstripe version: 3.4.0
 * OverrideTest.yml


ExtMember:
  ext_member:
    Email: ext@email.com
    Password: extpassword

 */


class ExtMember extends Member {}

class OverrideTest extends SapphireTest
{
    protected static $fixture_file = 'OverrideTest.yml';

    public function testBrokenFixtures()
    {
        $MockExtMember = $this->getMockBuilder('ExtMember')->getMock();


        $extMember     = $this->objFromFixture("ExtMember", "ext_member");
        Injector::inst()->registerService($MockExtMember, 'ExtMember');
        $extMemberNull = $this->objFromFixture("ExtMember", "ext_member");


        $this->assertEquals("ext@email.com", $extMember->Email);
        $this->assertNull($extMemberNull->Email);

    }
}