Mocking KafkaConsumer with pytest

Question

Recently I've been trying to learn unit testing and now I'm on the concept mocking. I'm writing my code with python and using pytest library to test my code. I've a simple factory class has only one function that creates a KafkaConsumer, and I want to test that function. This is the factory class:

from kafka import KafkaConsumer
import json

class KafkaFactory:
    
    @staticmethod
    def consumer(topic, group_id, server):
        return KafkaConsumer(
            topic,
            group_id=group_id,
            bootstrap_servers=server,
            auto_offset_reset='earliest',
            enable_auto_commit=False,
            value_deserializer=lambda v: json.loads(v.decode('utf-8'))
        )

This is my unit test:

from src.factories.kafka import KafkaFactory

class TestKafkaFactory:
    
    def test_consumer(self, mocker):
        mocker.patch('kafka.KafkaConsumer').return_value = 'consumer'
        spy_factory = mocker.spy(KafkaFactory, 'consumer')
        KafkaFactory.consumer('fake-topic', 'fake-group-id', 'fake-server')
        
        assert spy_factory.spy_return == 'consumer'

But when I run that test, I see that KafkaConsumer tries to connect a kafka client and I get NoBrokerAvailable expection. I've assumed that when I use mocker.patch method, it does not try to find a client and gives me a mock object. What am I missing? Thank you.

You are patching the wrong object, see [where to patch](https://docs.python.org/3/library/unittest.mock.html#id6). As you are using `from kafka import KafkaConsumer`, you have to patch `KafkaConsumer` in your factory module, e.g. something like `mocker.patch('kafka_factory.KafkaConsumer')`, if `kafka_factory` is the name of that module. — MrBean Bremen, Feb 20 '22 at 14:12

Mocking KafkaConsumer with pytest

0 Answers0