Add checks to unit test

The name of the test is now clearer and it checks the results for the first and
last items in the list.

tests/metrics/github/test_security.py

@@ -85,7 +85,7 @@ def test_security_number_of_alerts_last_year():
     assert result["open"] == 3
 
 
-def test_security_parse_vulnerabilities_earliest_date():
+def test_security_parse_vulnerabilities_earliest_and_latest_date():
     result = security.parse_vulnerabilities(
         fake_vulnerabilities("test-org"), "test-org"
     )
@@ -95,3 +95,5 @@ def test_security_parse_vulnerabilities_earliest_date():
     assert result[0]["closed"] == 0
     assert result[0]["open"] == 1
     assert str(result[-1]["date"]) == "2023-10-26"
+    assert result[-1]["closed"] == 4
+    assert result[-1]["open"] == 3