src/Concerns/HasHttpAssertions.php
public function assertFetchedToOne($id): self
    {
        $identifier = $this->identifier($id);

        $this->document = HttpAssert::assertFetchedToOne(
            $this->getStatusCode(),
            $this->getContentType(),
            $this->getContent(),
            $identifier['type'],
            $identifier['id']
        );

        return $this;
    }
public function assertFetchedToOne($id): self
    {
        $identifier = $this->identifier($id);

        $this->document = HttpAssert::assertFetchedToOne(
            $this->getStatusCode(),
            $this->getContentType(),
            $this->getContent(),
            $identifier['type'],
            $identifier['id']
        );

        return $this;
    }
Assert that a to-one relationship was fetched.

If either type or id are null, then it will be asserted that the data member of the content
is null.

Prov

@param UrlRoutable|string|int $id
@return $this