Escaped Mutant for Mutator "ConcatOperandRemoval": --- Original +++ New @@ @@ throw new InvalidListenerConfigurationException($this->createNotCallableMessage($listener)); } } catch (ContainerExceptionInterface $exception) { - throw new InvalidListenerConfigurationException('Could not instantiate event listener or listener class has invalid configuration. Got ' . $this->listenerDump($listener) . '.', 0, $exception); + throw new InvalidListenerConfigurationException('Could not instantiate event listener or listener class has invalid configuration. Got ' . $this->listenerDump($listener), 0, $exception); } } }