It appears that IRI values are not validated, as the URI values are.
In the /json-schema/tests/src/test/resources/org/everit/json/schema/draft7/optional/iri.json, I made a copy of the test to check as below. The tests pass contrary to expectations. Creating PR with a sample shortly.
{ "description": "an invalid IRI though valid IRI reference", "data": "âππ", "valid": false }, { "description": "an invalid IRI though valid IRI reference - copy", "data": "âππ", "valid": true }