Unable to mock variable in a function of a class

Question

I am trying to mock a class method that gets called within another class method.

from omdenalore.natural_language_processing.topic_modelling import TopicModelling
from unittest import mock


def test_process_words(load_spacy_model):
    tm = TopicModelling()
    with mock.patch.object(
        TopicModelling.process_words, "TextPreprocessor.load_model", return_value=load_spacy_model
    ):
        processed_words = tm.process_words()
        assert processed_words

TopicModelling class

from omdenalore.natural_language_processing.preprocess_text import (
    TextPreprocessor,
)

class TopicModelling:
    def __init__(self):
        ...
    def process_words(self):
        model = TextPreprocessor.load_model() # trying to mock this 
        # do some stuff with model

But I keep getting an error AttributeError: <function TopicModelling.process_words at 0x7fb1a2787c20> does not have the attribute 'TextPreprocessor.load_model'.

load_spacy_model is a fixture that I want to patch the function TextPreprocessor.load_model() with.

Similar question which I referred to.

Laurent · Accepted Answer · 2021-12-04 10:01:50Z

3

As I understand your code:

you are trying to patch the method TextPreprocessor.load_model, but instead you mock TopicModelling.process_words, and you do so in the namespace under test instead of that where TextPreprocessor.load_model is imported;
tm should be instantiated within the with statement, not before it.

So, I would suggest instead the following test script:

from omdenalore.natural_language_processing.topic_modelling import TopicModelling


def test_process_words(mocker):
    # Patch where load_model is called
    process_words = mocker.patch(
        "omdenalore.natural_language_processing.topic_modelling.TextPreprocessor.load_model",
        return_value=load_spacy_model,
    )
    # Instantiate and call
    tm = TopicModelling()
    processed_words = tm.process_words()

    assert processed_words

answered Dec 4, 2021 at 10:01

Laurent

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1 Comment

yudhiesh Over a year ago

I needed to install pytest-mock, then use load_spacy_model() which is a fixture as I previously used it to monkeypatch which needed to yield a function. Now it works!

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