Mockito is a spying framework originally based on the Java library with the same name.

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Install

pip install mockito

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

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 argument matchers:

# Use the Ellipsis, if you don't care
when(deferred).defer(...).thenRaise(Timeout)

# 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'))

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

Read

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