How to coverage my Python code with unittest

Question

I have some python code and I want to coverage it with unittest. My simple code is:

import os
import glob


class GitRepoParser:

    def __init__(self, repo_dir: str):
        self.repo_dir = repo_dir

    def get_folder_path(self, service_name: str) -> str:
        dir_path = '{path}/configuration/settings/{name}'.format(
            path=self.repo_dir,
            name=service_name
        )

        return dir_path

    def create_new_service(self, service_name: str, service_version: str):
        dir_path = self.get_folder_path(service_name)

        if os.path.isdir(dir_path):
            return

        os.makedirs(dir_path)
        property_file = '{folder}/{name}-deployment.properties'.format(
            folder=dir_path,
            name=service_name
        )

        current_path = os.path.dirname(__file__)
        template_path = os.path.join(
            current_path, '..', 'file_templates/deployment.properties'
        )

        if not os.path.isfile(template_path):
            return

        template_file = open(template_path, 'r')
        with open(property_file, 'w') as properties:
            for line in template_file:
                # Create parser for this code part
                value = line.strip().replace(
                    '%service_name%', service_name
                )

                properties.write(value + '\n')

        template_file.close()

Help me to create some unittest for this lines of code. I create some class GitRepoParserTest in my python tests:

class GitRepoParserTest(unittest.TestCase):
    def setUp(self):
        self.app = create_app('testing')
        self.app_context = self.app.app_context()
        self.app_context.push()
        self.parser = GitRepoParser('/path-to-download')

    def test_get_folder_path(self):
        folder_path = self.parser.get_folder_path(service_name='oleg-service')
        self.assertIsInstance(folder_path, str)

    def test_create_new_service(self):
        pass

But I don't understand how I need to write tests for create_new_service function.

Please help me.

Thank you.

understanding the input of the function (pre-condition) and expected output/side effect (post condition) may guide you in the right direction — rokpoto.com
– rokpoto.com, Commented Oct 14, 2019 at 22:06
Call create_new_service, afterwards open the target property file and verify it has the correct contents. — hoefling
– hoefling, Commented Oct 15, 2019 at 8:58
Does this really relate to pytest? I'm asking because this affects the approach you would need to take (mocking, temporary directories, etc.). — tmt
– tmt, Commented Oct 15, 2019 at 10:19

Lin Du · Accepted Answer · 2019-12-11 09:46:39Z

Here is the unit test solution for Python 3.7.5:

test_GitRepoParser.py:

import unittest
from unittest.mock import Mock, patch, mock_open, call
from GitRepoParser import GitRepoParser, os


class GitRepoParserTest(unittest.TestCase):
    def setUp(self):
        self.parser = GitRepoParser('/path-to-download')
        self.mock_open = mock_open(read_data='some data')

    def test_get_folder_path(self):
        folder_path = self.parser.get_folder_path(service_name='oleg-service')
        self.assertIsInstance(folder_path, str)

    @patch('GitRepoParser.os')
    def test_create_new_service_read_and_write_file_correctly(self, mock_os):
        mock_path = Mock()
        mock_path.dirname.return_value = '/Users/foo'
        mock_path.isdir.return_value = False
        mock_path.join.return_value = '/Users/whatever'
        mock_path.isfile.return_value = True
        mock_os.path = mock_path
        mock_os.makedirs = Mock()

        with patch('GitRepoParser.open', self.mock_open):
            self.parser.create_new_service(service_name='oleg-service', service_version='1.0')
            mock_path.isdir.assert_called_with('/path-to-download/configuration/settings/oleg-service')
            mock_os.makedirs.assert_called_with('/path-to-download/configuration/settings/oleg-service')
            expected = [call('/Users/whatever', 'r'),
                        call('/path-to-download/configuration/settings/oleg-service/oleg-service-deployment.properties', 'w')]
            self.mock_open.assert_has_calls(expected)
            handle = self.mock_open()
            handle.write.assert_called()
            handle.close.assert_called_once()

    @patch('GitRepoParser.os')
    def test_create_new_service_do_nothing_if_dir_path_is_dir(self, mock_os):
        mock_path = Mock()
        mock_path.isdir.return_value = True
        mock_os.path = mock_path
        mock_os.makedirs = Mock()

        self.parser.create_new_service(service_name='oleg-service', service_version='1.0')
        mock_path.isdir.assert_called_with('/path-to-download/configuration/settings/oleg-service')
        mock_os.makedirs.assert_not_called()


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

Unit test result with coverage report:

...
----------------------------------------------------------------------
Ran 3 tests in 0.023s

OK
Name                                               Stmts   Miss  Cover   Missing
--------------------------------------------------------------------------------
src/stackoverflow/58384586/GitRepoParser.py           24      1    96%   35
src/stackoverflow/58384586/test_GitRepoParser.py      37      0   100%
--------------------------------------------------------------------------------
TOTAL                                                 61      1    98%

As you can see, there is still a if condition branch left. You can finish it by yourself.

Source code: https://github.com/mrdulin/python-codelab/tree/master/src/stackoverflow/58384586

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