Fake implementation of redis API for testing purposes.
Project description
fakeredis: A fake version of a redis-py
fakeredis is a pure-Python implementation of the redis-py python client that simulates talking to a redis server. This was created for a single purpose: to write unittests. Setting up redis is not hard, but many times you want to write unittests that do not talk to an external server (such as redis). This module now allows tests to simply use this module as a reasonable substitute for redis.
Although fakeredis is pure Python, you will need lupa if you want to run Lua
scripts (this includes features like redis.lock.Lock, which are implemented
in Lua). If you install fakeredis with pip install fakeredis[lua] it will
be automatically installed.
Alternatives
Consider using redislite instead of fakeredis. It runs a real redis server and connects to it over a UNIX domain socket, so it will behave just like a real server. Another alternative is birdisle, which runs the redis code as a Python extension (no separate process), but which is currently unmaintained.
How to Use
The intent is for fakeredis to act as though you're talking to a real redis server. It does this by storing state internally. For example:
>>> import fakeredis
>>> r = fakeredis.FakeStrictRedis()
>>> r.set('foo', 'bar')
True
>>> r.get('foo')
'bar'
>>> r.lpush('bar', 1)
1
>>> r.lpush('bar', 2)
2
>>> r.lrange('bar', 0, -1)
[2, 1]
The state is stored in an instance of FakeServer. If one is not provided at
construction, a new instance is automatically created for you, but you can
explicitly create one to share state:
>>> import fakeredis
>>> server = fakeredis.FakeServer()
>>> r1 = fakeredis.FakeStrictRedis(server=server)
>>> r1.set('foo', 'bar')
True
>>> r2 = fakeredis.FakeStrictRedis(server=server)
>>> r2.get('foo')
'bar'
>>> r2.set('bar', 'baz')
True
>>> r1.get('bar')
'baz'
>>> r2.get('bar')
'baz'
It is also possible to mock connection errors so you can effectively test
your error handling. Simply set the connected attribute of the server to
False after initialization.
>>> import fakeredis
>>> server = fakeredis.FakeServer()
>>> server.connected = False
>>> r = fakeredis.FakeStrictRedis(server=server)
>>> r.set('foo', 'bar')
ConnectionError: FakeRedis is emulating a connection error.
>>> server.connected = True
>>> r.set('foo', 'bar')
True
Fakeredis implements the same interface as redis-py, the
popular redis client for python, and models the responses
of redis 6.2 (although most new features are not supported).
Support for aioredis
You can also use fakeredis to mock out aioredis. This is a much newer addition to fakeredis (added in 1.4.0) with less testing, so your mileage may vary. Both version 1 and version 2 (which have very different APIs) are supported. The API provided by fakeredis depends on the version of aioredis that is installed.
aioredis 1.x
Example:
>>> import fakeredis.aioredis
>>> r = await fakeredis.aioredis.create_redis_pool()
>>> await r.set('foo', 'bar')
True
>>> await r.get('foo')
b'bar'
You can pass a FakeServer as the first argument to create_redis or
create_redis_pool to share state (you can even share state with a
fakeredis.FakeRedis). It should even be safe to do this state sharing between
threads (as long as each connection/pool is only used in one thread).
It is highly recommended that you only use the aioredis support with Python 3.5.3 or higher. Earlier versions will not work correctly with non-default event loops.
aioredis 2.x
Example:
>>> import fakeredis.aioredis
>>> r = fakeredis.aioredis.FakeRedis()
>>> await r.set('foo', 'bar')
True
>>> await r.get('foo')
b'bar'
The support is essentially the same as for redis-py e.g., you can pass a
server keyword argument to the FakeRedis constructor.
Unimplemented Commands
All of the redis commands are implemented in fakeredis with these exceptions:
server
- acl load
- acl save
- acl list
- acl users
- acl getuser
- acl setuser
- acl deluser
- acl cat
- acl genpass
- acl whoami
- acl log
- acl help
- bgrewriteaof
- command
- command count
- command getkeys
- command info
- config get
- config rewrite
- config set
- config resetstat
- debug object
- debug segfault
- info
- lolwut
- memory doctor
- memory help
- memory malloc-stats
- memory purge
- memory stats
- memory usage
- module list
- module load
- module unload
- monitor
- role
- shutdown
- slaveof
- replicaof
- slowlog
- sync
- psync
- latency doctor
- latency graph
- latency history
- latency latest
- latency reset
- latency help
connection
- auth
- client caching
- client id
- client kill
- client list
- client getname
- client getredir
- client pause
- client reply
- client setname
- client tracking
- client unblock
- hello
- quit
string
- bitfield
- bitop
- bitpos
- stralgo
sorted_set
- bzpopmin
- bzpopmax
- zpopmax
- zpopmin
cluster
- cluster addslots
- cluster bumpepoch
- cluster count-failure-reports
- cluster countkeysinslot
- cluster delslots
- cluster failover
- cluster flushslots
- cluster forget
- cluster getkeysinslot
- cluster info
- cluster keyslot
- cluster meet
- cluster myid
- cluster nodes
- cluster replicate
- cluster reset
- cluster saveconfig
- cluster set-config-epoch
- cluster setslot
- cluster slaves
- cluster replicas
- cluster slots
- readonly
- readwrite
generic
- migrate
- object
- touch
- wait
geo
- geoadd
- geohash
- geopos
- geodist
- georadius
- georadiusbymember
list
- lpos
pubsub
- pubsub
scripting
- script debug
- script kill
stream
- xinfo
- xadd
- xtrim
- xdel
- xrange
- xrevrange
- xlen
- xread
- xgroup
- xreadgroup
- xack
- xclaim
- xpending
Other limitations
Apart from unimplemented commands, there are a number of cases where fakeredis won't give identical results to real redis. The following are differences that are unlikely to ever be fixed; there are also differences that are fixable (such as commands that do not support all features) which should be filed as bugs in Github.
-
Hyperloglogs are implemented using sets underneath. This means that the
typecommand will return the wrong answer, you can't usegetto retrieve the encoded value, and counts will be slightly different (they will in fact be exact). -
When a command has multiple error conditions, such as operating on a key of the wrong type and an integer argument is not well-formed, the choice of error to return may not match redis.
-
The
incrbyfloatandhincrbyfloatcommands in redis use the Clong doubletype, which typically has more precision than Python'sfloattype. -
Redis makes guarantees about the order in which clients blocked on blocking commands are woken up. Fakeredis does not honour these guarantees.
-
Where redis contains bugs, fakeredis generally does not try to provide exact bug-compatibility. It's not practical for fakeredis to try to match the set of bugs in your specific version of redis.
-
There are a number of cases where the behaviour of redis is undefined, such as the order of elements returned by set and hash commands. Fakeredis will generally not produce the same results, and in Python versions before 3.6 may produce different results each time the process is re-run.
-
SCAN/ZSCAN/HSCAN/SSCAN will not necessarily iterate all items if items are deleted or renamed during iteration. They also won't necessarily iterate in the same chunk sizes or the same order as redis.
-
DUMP/RESTORE will not return or expect data in the RDB format. Instead the
picklemodule is used to mimic an opaque and non-standard format. WARNING: Do not use RESTORE with untrusted data, as a malicious pickle can execute arbitrary code.
Contributing
Contributions are welcome. Please see the contributing guide for more details. The maintainer generally has very little time to work on fakeredis, so the best way to get a bug fixed is to contribute a pull request.
If you'd like to help out, you can start with any of the issues
labeled with Help wanted.
Running the Tests
To ensure parity with the real redis, there are a set of integration tests that mirror the unittests. For every unittest that is written, the same test is run against a real redis instance using a real redis-py client instance. In order to run these tests you must have a redis server running on localhost, port 6379 (the default settings). WARNING: the tests will completely wipe your database!
First install the requirements file::
pip install -r requirements.txt
pip install -r requirements-dev.txt
To run all the tests::
pytest
If you only want to run tests against fake redis, without a real redis::
pytest -m fake
Because this module is attempting to provide the same interface as redis-py,
the python bindings to redis, a reasonable way to test this to to take each
unittest and run it against a real redis server. fakeredis and the real redis
server should give the same result. To run tests against a real redis instance
instead::
pytest -m real
If redis is not running and you try to run tests against a real redis server, these tests will have a result of 's' for skipped.
There are some tests that test redis blocking operations that are somewhat slow. If you want to skip these tests during day to day development, they have all been tagged as 'slow' so you can skip them by running::
pytest -m "not slow"
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