How to test if else function by Unit test?

Question

I have a YAML config file used to check connection to database. I need to write some test cases for my config file includes several scenarios :

1. If the database field is empty then the test case fails.
2. If the database is not Sqlite or Postgre, test case fails.

I have created a test class but I don't know how to implement it. Can anyone suggest to me ?

data_source.yml:

database: 

dbopt:
   host: bvcbvcbvcb.com
   port: 5432
   dbname: db1
   user: username
   password: 1234
   client_encoding: utf-8
   connect_timeout: 60
   sslmode: none

query:
   select * from manufacturing_product

data_source.py:

import yaml

class InvalidConfigError(Exception):
    pass

class DB():
    def __init__(self, dbconf):
        self._dbconf = dict(dbconf)
        # checking for database type
        dbtype = self.get_db_type()
        if dbtype != 'sqlite' and dbtype != 'postgres':
            raise InvalidConfigError(
                'E01001', 'Invalid database type, should be sqlite or postgres.')
        else:
            self.dbtype = dbtype

    def get_db_type(self):
        return self._dbconf['database']

with open('data_source.yml') as f:
    data = yaml.full_load(f)

    for item, doc in data.items():
        print(item, ":", doc)

    database = DB(data)

My test class:

import yaml
import unittest
import data_source

class TestDBtype(unittest.TestCase):
    def test_missing_db(self):
        # if database is None then failed
        # What should I do?
        pass
    def test_db_type(self):
        # if database is not Sqlite or Postgres then failed
        # What should I do?
        pass
if __name__ == '__main__':
    unittest.main()

Answer 1

You can use like below. Idea is to initialize DB once and use the connection instance in test cases. I have not tested, but this is the idea.

import data_source


class TestDBtype(unittest.TestCase):

    #setUpClass gets calls only once where as setUp gets called before every test
    @classmethod
    def setUpClass(cls):
        cls.init_db()

    @classmethod
    def init_db(cls):
        self.db_instance = data_source.DB( config_file )



    def test_missing_db(self):
        self.assertEqual( db_instance, None, "Connection returned None.")