Reference library

Streaming & messaging

Kafka-style pub/sub, event consumers, async pipelines, and message-driven workflows.

4 matches

How to Mock NATS Subject Hierarchies with Wildcards in Python

Build a lightweight NATS-style pub/sub mock that matches subject hierarchies with '*' and '>' wildcards for tests or prototypes.

nats pubsub wildcards

Python

# Mock a simplified NATS subject hierarchy with wildcard matching
# Supports: exact match, '*' (single token), '>' (tail wildcard)

class NATSSubjectMock:
    def __init__(self):
        self.subscriptions = {}  # subject -> list of callbacks

    def subscribe(self, subject, callback):
        self.subscriptions.setd…

13 0 Open

Streaming & messaging medium

How to Mock a Kafka Producer Batch Send in Python

Simulate a Kafka producer in Python that sends batched JSON events with mock partitions and latency for testing streaming pipelines without a real broker.

kafka mock streaming

Python

import json
import random
import time
from datetime import datetime


class MockKafkaProducer:
    def __init__(self, topic):
        self.topic = topic
        self.sent_messages = []

    def send(self, value, key=None):
        message = {
            "topic": self.topic,
            "key": key,
            "value"…

13 0 Open

Streaming & messaging medium

How to Mock a Kafka Rebalance Listener in Python

Simulate Kafka consumer rebalance callbacks (on_partitions_revoked and on_partitions_assigned) with a mock consumer to test listener logic.

kafka rebalance mocking

Python

import time
from collections import defaultdict


class MockKafkaConsumer:
    def __init__(self):
        self.assignments = defaultdict(list)
        self.rebalances = 0

    def assign(self, partitions):
        self.rebalances += 1
        self.assignments.clear()
        for partition in partitions:
            s…

15 0 Open

Streaming & messaging medium

Mock Redis Streams XADD and XREAD in Python

A pure-Python mock of Redis streams that implements basic XADD, XREAD, and XLEN behavior for local testing without a real Redis server.

redis streams mocking

Python

import redis
import time
import threading


class MockRedisStreams:
    def __init__(self):
        self.streams = {}

    def xadd(self, stream_name, fields):
        if stream_name not in self.streams:
            self.streams[stream_name] = []
        entry_id = f"{time.time_ns()}-{len(self.streams[stream_name])}"
…

13 0 Open

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