Escaped Mutant for Mutator "InstanceOf_": --- Original +++ New @@ @@ } $classMetadataOfFieldValue = $this->entityManager->getClassMetadata($fieldValue::class); $collection = $classMetadataOfFieldValue->getFieldValue($fieldValue, $inversedBy); - if (!$collection instanceof Common\Collections\Collection) { + if (!true) { return; } $collection->add($entity);