Unit testing Mock GCS

I have a hard time to find a way to make a unit test for the read and write methods present in this class. I am trying to create a mock with the mock patch library in order to avoid calling Google Storage but I have a hard time figure out how to do it.

from google.cloud import storage


class GCSObject(str):
    

    def __init__(self, uri=""):
        self.base, self.bucket, self.path = self.parse_uri(uri)


    def parse_uri(self, uri):
        uri = uri.lstrip("gs://").replace("//", "/").split("/", 1)
        if len(uri) > 1:
            return ("gs://", uri[0], uri[1])
        else:
            return ("gs://", uri[0], "")

    def read(self) -> bytes:
        storage_client = storage.Client()
        bucket = storage_client.bucket(self.bucket)
        return bucket.blob(self.path).download_as_string()

    def write(self, content: bytes):
        storage_client = storage.Client()
        bucket = storage_client.get_bucket(self.bucket)
        blob = bucket.blob(self.path)
        blob.upload_from_string(content)

What I am currently trying to do

@mock.patch("packages.pyGCP.pyGCP.gcs.storage.Client")
def test_upload(client):
    gcs_path = GCSObject("fake_path")
    reader = gcs_path.read()  
    #  confused what I should assert