[review] use concrete instance of Checksum instead fixture

squash with [issue-456] add external document parser

Signed-off-by: Meret Behrens <meret.behrens@tngtech.com>

Author: Meret Behrens

tests/spdx/parser/rdf/test_creation_info_parser.py

@@ -15,8 +15,7 @@
 import pytest
 from rdflib import Graph, RDF, URIRef
 from rdflib.term import Node
-
-from tests.spdx.fixtures import checksum_fixture
+from spdx.model.checksum import Checksum, ChecksumAlgorithm
 
 from spdx.model.version import Version
 
@@ -79,5 +78,6 @@ def test_parse_external_document_refs():
     external_document_ref = parse_external_document_refs(external_doc_ref_node, graph, doc_namespace)
 
     assert external_document_ref.document_ref_id == "DocumentRef-external"
-    assert external_document_ref.checksum == checksum_fixture()
+    assert external_document_ref.checksum == Checksum(ChecksumAlgorithm.SHA1,
+                                                      "71c4025dd9897b364f3ebbb42c484ff43d00791c")
     assert external_document_ref.document_uri == "https://namespace.com"