pytest throws exception while using ClickArguments SystemExit: 0

I am trying to run a test case for a python script. Test case is successful when I don’t use Click decorator and argument in python script method.

But when I am using it, it gives SystemExit: 0.

cleanup.py:

import boto3
import sys
import click

ec2=boto3.client("ec2")

@click.command()
@click.argument('ami_info',nargs=-1)
def get_all_amis(ami_info):
    print("amis_to_retain --> {}".format(ami_info[1]))
    print("amis_name_prefix --> {}".format(ami_info[0]))
    amis=ec2.describe_images(Owners=["self"])
    return amis

test_cleanup.py:

import boto3
import sys
import botocore.session
from botocore.stub import Stubber
import pytest
import cleanup

@pytest.fixture(autouse=False)
def stub_ec2():
    ec2_stubber = boto3.client("ec2")
    stubber = Stubber(ec2_stubber)
    cleanup.ec2=ec2_stubber
    yield stubber
    try:
        stubber.deactivate()
    except:
        print("ec2 Stubber already deactivated")

def test_ami_list(stub_ec2):
    stub_ec2.add_response(
        'describe_images',
        expected_params={'Owners':['self']},
        service_response={"Images": [{"ImageId": "DummyVal"}]}
    )
    stub_ec2.activate()
    response = cleanup.get_all_amis(["ctm","10"])
    print("response is --> {}".format(response))

I am running test case per below

pytest -rA tests

where tests is the directory where both above files are kept.

Test fails with SystemExit: 0

>Solution :

Don’t run click commands directly; they will use sys.exit(0) when done.

Instead, follow the Testing Click Applications chapter and use CliRunner() object to run your commands:

from click.testing import CliRunner
# ...


def test_ami_list(stub_ec2):
    stub_ec2.add_response(
        'describe_images',
        expected_params={'Owners':['self']},
        service_response = {"DummyKey":"DummyVal"}
    )
    stub_ec2.activate()

    runner = CliRunner()
    result = runner.invoke(cleanup.get_all_amis, ["ctm", "10"])
    response = result.return_value

Note that I passed in a list of string arguments; click will parse those into the correct structure.