Patch test syntax for validating identifier system value

Before performing an add or replace, we need to test to see whether an identifier array/system value exists. We can’t find documentation that would show how to do this. I wanting to do something like:
“op”: “test”,
“path”: “/identifier[?(system:exact=urn:company:somevalue)”,
“value”: true
fhir tells me the target location specified by the path segment was not found.

Have you looked at the Conditional Create and Conditional Update capabilities?