def METHOD_NAME():
    document = document_fixture(
        relationships=[Relationship("SPDXRef-Package", RelationshipType.DESCRIBES, "SPDXRef-File")]
    )
    validation_messages: List[ValidationMessage] = validate_full_spdx_document(document)
    assert validation_messages == [
        ValidationMessage(
            f'there must be at least one relationship "{DOCUMENT_SPDX_ID} DESCRIBES ..." or "... DESCRIBED_BY '
            f'{DOCUMENT_SPDX_ID}" when there is not only a single package present',
            ValidationContext(spdx_id=DOCUMENT_SPDX_ID, element_type=SpdxElementType.DOCUMENT),
        )
    ]