Mocking a global variable
Solution 1
Try this:
import unittests
import alphabet
from unittest import mock
class TestAlphabet(unittest.TestCase):
def setUp(self):
self.mock_letters = mock.patch.object(
alphabet, 'letters', return_value=['a', 'b', 'c']
)
def test_length_letters(self):
with self.mock_letters:
self.assertEqual(3, alphabet.length_letters())
def test_contains_letter(self):
with self.mock_letters:
self.assertTrue(alphabet.contains_letter('a'))
You need to apply the mock while the individual tests are actually running, not just in setUp()
. We can create the mock in setUp()
, and apply it later with a with ...
Context Manager.
Solution 2
Variables can be patched as follows:
from mock import patch
@patch('module.variable', new_value)
For example:
import alphabet
from mock import patch
@patch('alphabet.letters', ['a', 'b', 'c'])
class TestAlphabet():
def test_length_letters(self):
assert 3 == alphabet.length_letters()
def test_contains_letter(self):
assert alphabet.contains_letter('a')
Solution 3
I ran into a problem where I was trying to mock out variables that were used outside of any function or class, which is problematic because they are used the moment you try to mock the class, before you can mock the values.
I ended up using an environment variable. If the environment variable exists, use that value, otherwise use the application default. This way I could set the environment variable value in my tests.
In my test, I had this code before the class was imported
os.environ["PROFILER_LOG_PATH"] = "./"
In my class:
log_path = os.environ.get("PROFILER_LOG_PATH",config.LOG_PATH)
By default my config.LOG_PATH
is /var/log/<my app name>
, but now when the test is running, the log path is set to the current directory. This way you don't need root access to run the tests.
Funkatic
Updated on July 05, 2022Comments
-
Funkatic almost 2 years
I've been trying to implement some unit tests for a module. An example module named alphabet.py is as follows:
import database def length_letters(): return len(letters) def contains_letter(letter): return True if letter in letters else False letters = database.get('letters') # returns a list of letters
I'd like to mock the response from a database with some values of my choice, but the code below doesn't seem to work.
import unittests import alphabet from unittest.mock import patch class TestAlphabet(unittest.TestCase): @patch('alphabet.letters') def setUp(self, mock_letters): mock_letters.return_value = ['a', 'b', 'c'] def test_length_letters(self): self.assertEqual(3, alphabet.length_letters()) def test_contains_letter(self): self.assertTrue(alphabet.contains_letter('a'))
I have seen many examples in which 'patch' is applied to methods and classes, but not to variables. I prefer not to patch the method database.get because I may use it again with different parameters later on, so I would need a different response.
What am I doing wrong here?