How to mock a redis client in Python?

Question

I just found that a bunch of unit tests are failing, due a developer hasn't mocked out the dependency to a redis client within the test. I'm trying to give a hand in this matter but have difficulties myself.

The method writes to a redis client:

redis_client = get_redis_client()
redis_client.set('temp-facility-data', cPickle.dumps(df))

Later in the assert the result is retrieved:

res = cPickle.loads(get_redis_client().get('temp-facility-data'))
expected = pd.Series([set([1, 2, 3, 4, 5])], index=[1])
assert_series_equal(res.variation_pks, expected)

I managed to patch the redis client's get() and set() successfully.

@mock.patch('redis.StrictRedis.get')
@mock.patch('redis.StrictRedis.set')
def test_identical(self, mock_redis_set, mock_redis_get):
    mock_redis_get.return_value = ???
    f2 = deepcopy(self.f)
    f3 = deepcopy(self.f)
    f2.pk = 2
    f3.pk = 3
    self.one_row(f2, f3)

but I don't know how to set the return_value of get() to what the set() would set in the code, so that the test would pass.

Right now this line fails the test:

res = cPickle.loads(get_redis_client().get('temp-facility-data'))
TypeError: must be string, not MagicMock

Any advice please?

use side_effect with a shared object being set in the set side_effect and returned in get side_effect? docs.python.org/3/library/unittest.mock.html#quick-guide — user3012759
– user3012759, Commented May 29, 2015 at 14:24

user3012759 · Accepted Answer · 2015-05-29 14:35:37Z

29

Think you can use side effect to set and get value in a local dict

data = {}
def set(key, val):
    data[key] = val

def get(key):
    return data[key]

mock_redis_set.side_effect = set
mock_redis_get.side_effect = get

not tested this but I think it should do what you want

answered May 29, 2015 at 14:35

user3012759

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2 Comments

cglacet Over a year ago

Can you give a little bit more context? (write a complete test, with mock creation, actual get/set usage in a code that you test). Also, how do you prevent connection from crashing, I guess that even if you mock get/set, pool connections (and any other network related connection) will still crash.

Ajite Over a year ago

Thank you for sharing. I found out that using get is better since using a non-existing key on REDIS does not raise exception. ``` def get(key): return data.get(key) ```

Christopher Hart · Accepted Answer · 2023-11-15 09:42:12Z

8

If you want something more complete, you can try fakeredis

@patch("redis.Redis", return_value=fakeredis.FakeStrictRedis())
def test_something():
....

edited Nov 15, 2023 at 9:42

Christopher Hart

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answered Nov 18, 2021 at 18:14

Narek

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1 Comment

SagarM Over a year ago

"Fakeredis has moved". New maintainer: github.com/cunla/fakeredis-py

Akarshan · Accepted Answer · 2022-01-02 20:09:53Z

1

I think you can do something like this.

redis_cache = {
    "key1": (b'\x80\x04\x95\x08\x00\x00\x00\x00\x00\x00\x00\x8c\x04test\x94.', "test"),
    "key2": (None, None),
}
    
def get(redis_key):
    if redis_key in redis_cache:
        return redis_cache[redis_key][0]
    else:
        return None
    
mock = MagicMock()
mock.get = Mock(side_effect=get)
    
with patch('redis.StrictRedis', return_value=mock) as p:
    for key in redis_cache:
        result = self.MyClass.my_function(key)
        self.assertEqual(result, redis_cache[key][1])

answered Jan 2, 2022 at 20:09

Akarshan

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