Another important assertion, assertRaises is used to catch exceptions.
assertRaises tries to check if a specified Exception is raised, when the test runs.
The test passes, if the specified exception is raised or else it fails.
The below shown test test_sample1 written in another module test_module2.py catches TypeError raised while adding an integer and a string.
from proj.sample_module import add2num
import unittest
class SampleTestClass(unittest.TestCase):
def test_sample1(self):
self.assertRaises(TypeError, add2num, 3, 'hello')
Running the above test with below command, passes the test.
python -m unittest test.test_module2
You can also use with for catching exceptions.
The previous example can be written as shown below.
from proj.sample_module import add2num
import unittest
class SampleTestClass(unittest.TestCase):
def test_sample1(self):
with self.assertRaises(TypeError) as e:
r = add2num(3, 'hello')
self.assertEqual(str(e.exception), "unsupported operand type(s) for +: 'int' and 'str'")
The example also validates the error message, which is displayed.
