Testing lambdas (Python) with aws-cdk?

Question

I want to setup unit tests for my lambdas that are written in Python. I am using aws-cdk to develop and deploy my lambdas. How do I propperly setup these unit tests? Which libraries do I use? How to put it in a packet structure? Maybe an example can clarify.

I was looking into the library 'unittest'. I set up a folder names 'test' and put a test file in there named: test_first.py. I could then execute all test files in this folder by using the command: python -m unittest discover ./test

test_first.py

import unittest

class FirstTest(unittest.TestCase):
    def test_default(self):
        self.assertEqual(10, (5+5))

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

Is this the right way to do this? I now have the problem that I don't know how to import another python file and test its methods in this file. This would be the lambda I have written and test its methods. How do I do this?

Answer 1

Lambda python files are just like any other python files whose methods can be tested as unit tests. Below is a simple example

import unittest

from my_sum import sum


class TestSum(unittest.TestCase):
    def test_list_int(self):
        """
        Test that it can sum a list of integers
        """
        data = [1, 2, 3]
        result = sum(data)
        self.assertEqual(result, 6)

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

You can import your lambda method like we imported sum from my_sum and then write some asserts on it. This document is a good read for the same.