public function testGetDefaultHelperReturnsDefinedDefaultHelper()
 {
     $helperA = $this->prophesize(InstanceHelper::class);
     $helperB = $this->prophesize(InstanceHelper::class);
     $helperRegistry = new InstanceHelperRegistry();
     $helperRegistry->addHelper('helperA', $helperA->reveal());
     $helperRegistry->addHelper('helperB', $helperB->reveal());
     $helperRegistry->setDefaultHelper('helperB');
     $this->assertSame($helperB->reveal(), $helperRegistry->getDefaultHelper());
 }