Unittesting CODESYS python scripts

2020-02-27T14:48:30.139000Z

I've managed to solve this myself. Rather than battering my head trying to work out how to mock a global like librarymanager, I have created a class to wrap the codesys interface, and used dependency injection to pass this to my script. I can then create a mock using mock.create_autospec(CodesysInterface). A much nicer solution...

Unittesting CODESYS python scripts

2020-02-27T14:48:28.514000Z

Please forgive my if this is obvious, I'm not a python expert. I have some scripts that work inside CODESYS, but I need to extend them and I want them to be maintainable, so I want to introduce a Unittest framework around the modules before refactoring and then adding more code.

I want my unit tests to be fast so that I can use TDD, so I don't want to work inside CODESYS. Instead I want to work using activepython and to be able to use the features of mock and mock.patch to replace the CODESYS API calls. But I haven't yet managed to get this to work.

As an example I have created a cutdown example using a couple of very simple files
Vendor.py

class Vendor(object):
    def __init__(self, name):
        self.name = name

TestVendor.py

import mock
import unittest
import Vendor
class TestVendor(unittest.TestCase):
    
    def testName(self):
        vendor = Vendor.Vendor('VendorName')
        self.assertEqual('VendorName', vendor.name)
        
if __name__ == "__main__":
    #import sys;sys.argv = ['', 'Test.testName']
    unittest.main()

This simple test runs and passes.

I want to add some functionality that uses the librarymanager, the first test that I want is to verify that there is a single call to , when I create a Vendor object. One of my many attempts starts like this, I've just tried to declare the module I am mocking, no actual test.

    @mock.patch('librarymanager')
    def testGetAllLibrariesCalled(self):
        '''
        '''

I get the following error when I try to run the test

Zitat:
TypeError: Need a valid target to patch. You supplied: 'librarymanager'

How would I write this first test? i.e. mock the module, mock the function, and assert that the function is called. I'm sure if I can get this first call tested the rest will be straightforward.

If I'm going down the wrong track, and I would be better trying this unit testing using different tools then please let me know.

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