test_default_value.py

import graphene

class Result(graphene.ObjectType):
    text = graphene.String(default_value="OK")
    code = graphene.Int()


class Queries(graphene.ObjectType):
    result = graphene.Field(Result)

    def resolve_result(root, info):
        return Result(code=200)


def test_default_value():
    query = """
        query {
            result {
                text
                code
            }
        }
    """
    schema = graphene.Schema(query=Queries)
    result = schema.execute(query)

    assert result.data["result"] == {'code': 200, 'text': 'OK'}