TypeError: object is not callable when instantiating during unit test

Question

I have a class that throws an exception when instantiated with wrong values and I would like to write a unit test raising an exception when given wrong parameters.

Instantiating an object outside of the self.assertRaises() doesn't seem to cause any error and I fail to understand why it causes an error when I try to instantiate it within the assert

my class looks like this:

class Mark:
    def __init__(self, a, b, c):
        try:
            self.a = a
            self.b = int(b)
            self.c = int(c)
        except ValueError:
            print(e)

My test looks like this:

import unittest
import main


class Test(unittest.TestCase):

    def test_marks(self):

        self.assertRaises(ValueError, main.Mark("X", 5, 32))
        self.assertRaises(ValueError, main.Mark(1, "X", 32))
        self.assertRaises(ValueError, main.Mark(1, 5, "X"))


if __name__ == "__main__":
    unittest.main()

But I get:

(base) ➜  Code Python3 test.py
E
======================================================================
ERROR: test_marks (__main__.Test)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Code/test.py", line 12, in test_marks
    self.assertRaises(ValueError, main.Mark("X", 5, 32))
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/unittest/case.py", line 733, in assertRaises
    return context.handle('assertRaises', args, kwargs)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/unittest/case.py", line 201, in handle
    callable_obj(*args, **kwargs)
TypeError: 'Mark' object is not callable

----------------------------------------------------------------------
Ran 1 test in 0.001s

FAILED (errors=1)

Do you know how should I do if I want to test this ?

Answer 1

assertRaises() expects a callable and not a called function.

You just give the callable and append the arguments without ():

self.assertRaises(ValueError, main.Mark, "X", 5, 32)

Alternatively you can use a context manager:

with self.assertRaises(ValueError):
    main.Mark("X", 5, 32)