BotoCore/Boto3 Stubber Operation Not Found for generate_presigned_post

Question

I'm trying to use the botocore.stub.Stubber to mock my boto3.client, and I am getting a botocore.model.OperationNotFoundError when trying to add the mocked generate_presigned_post response:

class S3FileTestCase(TestCase):

    @classmethod
    def setUpTestData(cls):
        cls.s3 = botocore.session.get_session().create_client('s3')
        cls.region_name = 'eu-west-2'

    @staticmethod
    def _mock__get_s3(region_name):
        client = boto3.client('s3', config=boto3.session.Config(signature_version='s3v4'), region_name=region_name)
        stubber = Stubber(client)

        stubber.add_response('generate_presigned_post', {'test':1}, {'bucket_name': 'test_bucket', 'region_name': region_name, 'object_name': 'test.csv'})
        return stubber

    @patch('uploader.models.s3_file.S3File._get_s3', new=_mock__get_s3)
    def test_create_presigned_post(self):
        response = S3File.create_presigned_post('stuart-special-testing-bucket', self.region_name, 'test.csv')
        print(response)

When I run test_create_presigned_post I get the OperationNotFoundError in the add_reponse. Does anyone have any idea why this might be?

Note: S3File.create_presigned_post is taken directly from the docs with the only change being that the client is moved into a function so it can be mocked (and adding a region parameter).

user_1683995 · Answer

generate_presigned_post() and generate_presigned_url() do not make API calls to S3, and therefore do not need the Stubber.

https://github.com/boto/botocore/blob/b3b5559a641c1caecaec2739564f043b61947d51/botocore/signers.py#L607

Example:

import boto3

s3 = boto3.client("s3")


def get_upload_url() -> dict:
    return s3.generate_presigned_post(
        Bucket="test-bucket",
        Key="test-file.txt",
    )


def test_get_upload_url():
    response: dict = get_upload_url()
    assert "url" in response
    assert "fields" in response

BotoCore/Boto3 Stubber Operation Not Found for generate_presigned_post

1 Answers