public function checkGenerated(): ?GeneratorVerifier
    {
        $cardinality = $this->resetCardinality()->assertSingular();

        if ($this->call->responseEvent()) {
            list(, $returnValue) = $this->call->response();

            $isMatch = $returnValue instanceof Generator;
        } else {
            $isMatch = false;
        }

        list($matchCount, $matchingEvents) =
            $this->matchIf($this->call, $isMatch);

        if ($cardinality->matches($matchCount, 1)) {
            return $this->assertionRecorder->createSuccessFromEventCollection(
                $this->generatorVerifierFactory
                    ->create($this->call, $matchingEvents)
            );
        }

        return null;
    }