Mockito¶

Mockito is a spying framework focusing on ergonomics.

Install¶

pip install mockito

If you already use pytest, consider using the plugin pytest-mockito too.

Use¶

from mockito import when, mock, unstub

when(os.path).exists('/foo').thenReturn(True)

# or:
import requests  # the famous library
# you actually want to return a Response-like obj, we'll fake it
response = mock({'status_code': 200, 'text': 'Ok'})
when(requests).get(...).thenReturn(response)

# use it
requests.get('http://google.com/')

# clean up
unstub()

Features¶

Super easy to set up different answers.

# Well, you know the internet
when(requests).get(...).thenReturn(mock({'status': 501})) \
                       .thenRaise(Timeout("I'm flaky")) \
                       .thenReturn(mock({'status': 200, 'text': 'Ok'}))

State-of-the-art, high-five chaining:

# SQLAlchemy, fluently
with when(User).query.filter_by(...).first().thenReturn("A user"):
    assert User.query.filter_by(username='admin').first() == "A user"

State-of-the-art, high-five argument matchers:

# Use the Ellipsis, if you don't care
when(deferred).defer(...).thenRaise(Timeout)
when(requests).get('https://example.com', headers=...)

# Or **kwargs
from mockito import kwargs  # or KWARGS
when(requests).get('http://my-api.com/user', **kwargs)

# The usual matchers
from mockito import ANY, or_, not_
number = or_(ANY(int), ANY(float))
when(math).sqrt(not_(number)).thenRaise(
    TypeError('argument must be a number'))

Captors:

args, kwargs = captor(), captor()
when(mamma).said(*args, **kwargs)
# use it ...
assert args.value == ("Knock", "You", "Out")

No need to verify (assert_called_with) all the time:

# Different arguments, different answers
when(foo).bar(1).thenReturn(2)
when(foo).bar(2).thenReturn(3)

# but:
foo.bar(3)  # throws immediately: unexpected invocation

# because of that you just know that when
# you get a `2`, you called it with `1`

Signature checking:

# when stubbing
when(requests).get()  # throws immediately: TypeError url required

# when calling
request.get(location='http://example.com/')  # TypeError

Property stubbing:

class Settings:
    @property
    def timeout(self):
        return 10

with when(Settings).timeout.thenReturn(5):
    assert Settings().timeout == 5

Full async/await support:

# Avoid internet side effects.
async def http_get(location: str, session: aiohttp.ClientSession) -> str:
    async with session.get(location, headers=headers, raise_for_status=True) as resp:
        return await resp.text()

when(module_under_test).http_get('https://example.com', ...).thenReturn('Yep!')

Convenience:

with patch_attr("sys.argv", ["foo", "bar"]):
with patch_attr("sys.stdout", StringIO()) as stdout: ...
with patch_dict(os.environ, {"user": "bob"}): ...

Read¶

Report issues, contribute more documentation or give feedback at Github!