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How to mock a fallback return value in Python
Test a function that returns a default value on failure by mocking requests.get and its side effects.
from unittest.mock import Mock, patch
import requests
def fetch_data(url, default=None):
try:
response = requests.get(url)
response.raise_for_status()
return response.json()
except (requests.RequestException, ValueError):
return default
with patch("requests.get") as mock_get:
…Mocking a Metrics Gauge's set_value Method in Python
Demonstrates using unittest.mock.Mock with wraps to intercept a gauge's set_value call while verifying arguments and preserving real behavior.
from unittest.mock import Mock
class MetricsGauge:
def __init__(self, name):
self.name = name
self.value = 0.0
def set_value(self, new_value):
self.value = float(new_value)
return self.value
# Usage demonstration with a mock
gauge = MetricsGauge("cpu_usage")
gauge_mock = Mock…How to Mock Hive Support in PySpark with unittest.mock
This code demonstrates how to mock Hive support in a PySpark environment using unittest.mock to simulate SQL queries returning fixed data.
from unittest.mock import Mock, patch
def get_hive_tables(spark):
"""Mock Hive support by returning a fixed list of tables."""
return spark.sql("SHOW TABLES").collect()
class HiveTable:
"""Simple class that mimics a Hive table row."""
def __init__(self, database, tableName):
self.database =…How to Mock MLflow log_params and log_metrics in Python
Use unittest.mock to patch MLflow's log_param and log_metric, run the training function, and verify logging calls without touching a real tracking server.
from unittest.mock import Mock, patch
import mlflow
def train_model():
mlflow.log_param("learning_rate", 0.01)
mlflow.log_param("epochs", 10)
mlflow.log_metric("accuracy", 0.95)
mlflow.log_metric("loss", 0.05)
return "Training completed"
if __name__ == "__main__":
with patch("mlflow.log_par…How to Create a Sticky Consistent Mock with unittest.mock in Python
Shows how to use unittest.mock.patch.object to mock a method consistently across multiple calls, returning a sticky value every time.
from unittest.mock import patch
class Database:
def fetch(self, key):
return f"real value for {key}"
def get_value(db, key):
return db.fetch(key)
if __name__ == "__main__":
db = Database()
with patch.object(db, "fetch", return_value="sticky value") as mock_fetch:
result1 = get_value(…How to Mock a Function Call in Python with unittest.mock
Use unittest.mock.Mock to wrap a function and spy on its call count and arguments in Python.
import random
from unittest.mock import Mock, patch
def select_n_plus_one(numbers: list[int]) -> int:
"""Return the first number that appears more than once, if any."""
seen = set()
for num in numbers:
if num in seen:
return num
seen.add(num)
return -1
def detect_mock(se…How to Mock a Dependency for Readiness Probe in Python
Use unittest.mock.Mock to simulate a dependency's readiness check response for testing a service's is_ready method without hitting a real connection.
import time
import unittest
from unittest.mock import Mock
class Service:
def __init__(self, dependency):
self.dependency = dependency
def is_ready(self):
try:
result = self.dependency.check()
return result == "ready"
except Exception:
return False
…How to Mock a Slow Startup Probe for Fast Testing in Python
This code shows how to replace a slow startup probe's initialization with a mock to make tests run fast and reliably.
import time
from unittest.mock import Mock, patch
class StartupProbe:
def __init__(self, init_time):
self.init_time = init_time
self.ready = False
def initialize(self):
time.sleep(self.init_time)
self.ready = True
return self.ready
def run_startup_probe(probe):
…How to Mock time.sleep in a Python PreStop Hook
This code simulates a Kubernetes PreStop hook that delays shutdown, then mocks time.sleep to verify the hook logic without real delay.
import subprocess
import sys
import time
from unittest.mock import patch
def pre_stop_hook():
"""Simulate a Kubernetes PreStop hook that sleeps before shutdown."""
print("PreStop hook started: delaying shutdown")
time.sleep(3)
print("PreStop hook completed: ready to shutdown")
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