CODEWITHSUNDEEP
pythonunit-testingmocking
New2Py
New2Py

Reputation: 23

mocking API calls in unit testing

I am fairly new to Python and having a hard time wrapping my head around how to mock patch API calls in unit testing. FYI, I am using Python 2.7 and using nosetest for my unit testing needs.

I have the following module (myRedis.py) which I want to unit test:

import logging
import redis

redispool = None

class myRedis(object):

def __init__(self, redisHost, redisPort, redisDBNum):
    if not redisPort.isdigit():
        raise TypeError('Exception: Expected int for redisPort')

    if not redisDBNum.isdigit():
        raise TypeError('Exception: Expected int for redisDBNum')

    self._redis_instance = None

    self._redishost = redisHost
    self._redisport = redisPort
    self._redisdb = redisDBNum

    global redispool
    redispool = redis.ConnectionPool(host=self._redishost,
                                          port=self._redisport,
                                          db=self._redisdb)

    def redis_connect(self):
         LOGGER.info('Connecting Redis client to %s:%s:%s', self._redishost,
         self._redisport, self._redisdb)
         self._redis_instance = redis.StrictRedis(connection_pool=redispool)

    def write_redis(self, key, value):
         retval = self._redis_instance.set(key, value)
         LOGGER.info('Writing data to redis (%s, %s). Retval=%s', key, value, retval)
         return retval

    def read_redis(self, key):
         retval = self._redis_instance.get(key) 
         LOGGER.info('Reading data from redis: key=%s. Retval=%s', key, retval)
         return retval

As far as unit testing goes, I have the following so far. 

from nose.tools import *
import mock
from myRedis import myRedis

def setup():
    pass
def teardown():
    pass

@mock.patch('redis.StrictRedis')
def test_mock_redis_StrictRedis(mock_conn_pool):
    mock_conn_pool.return_value = True
    assert(True)

def test_myRedis():

    assert_raises(TypeError, myRedis, 
              'test', '1234', 'a11')

    assert_raises(TypeError, myRedis, 
              'test', 'a1234', '11')

    myRedisObj = myRedis('localhost', '8888', '11')
    assert_equal(myRedisObj._redishost, 'localhost')
    assert_equal(myRedisObj._redisport, '8888')
    assert_equal(myRedisObj._redisdb, '11')

    myRedisObj.redis_connect()
    #oclRedis.read_redis('test')
    #oclRedis.write_redis('test', 'test')

I am able to patch the redis.StrictRedis() call without any problems. But how do I patch the redis' get() and set() calls since they are invoked on an object (_redis_instance in myRedis.py). I tried a few different versions of @mock.patch.object, but that didn't work for me. Looking for some guidance.

Thanks in advance.

Upvotes: 2

Views: 1049

Answers (1)

Enrique Saez
Enrique Saez

Reputation: 2700

What you should patch are not the actual calls from your object but actually the object itself that those calls are invoking.

In your code it would something along the lines of:

from nose.tools import *
import mock
import unittest
from red import myRedis

def setup():
    pass
def teardown():
    pass

@mock.patch('redis.StrictRedis')
def test_mock_redis_StrictRedis(mock_conn_pool):
    mock_conn_pool.return_value = True
    assert(True)

def test_myRedis_wrong_args():
    assert_raises(TypeError, myRedis,
              'test', '1234', 'a11')
    assert_raises(TypeError, myRedis,
              'test', 'a1234', '11')

def test_myRedis_ok():
    myRedisObj = myRedis('localhost', '8888', '11')
    assert_equal(myRedisObj._redishost, 'localhost')
    assert_equal(myRedisObj._redisport, '8888')
    assert_equal(myRedisObj._redisdb, '11')


@mock.patch('redis.StrictRedis.set')
def test_myRedis_write(mock_strict_redis_set):
    mock_strict_redis_set.return_value = {}
    myRedisObj = myRedis('localhost', '8888', '11')
    redis_connect = myRedisObj.redis_connect()
    connect = myRedisObj.write_redis('1', '2')
    assert connect == {}

As you can see I modified your tests to test one thing at a time. This is something that you generally want to do to avoid side-effects and guarantee test isolation.

Consider taking a look at the docs: https://docs.python.org/dev/library/unittest.mock.html

Finally indenting is key in Python, consider proper indenting in your code snippets going forward

Upvotes: 2

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