CODEWITHSUNDEEP
pythonpostgresqlunit-testingexception
ovod
ovod

Reputation: 1178

how to test exception in python working with postgresql

I have my own class Article designed to wrok with PostgreSQL. Each object created from the class is used to work with one row. Now I dont know how to test exception case. When I create such case:

article = Article(2)/*connects to the db and loads line with id 2*/
print article.title2 /*here my db does not have table title2 and should launch an error*/

it should throw error. And it does) How should test case looks like? I use unittest. My test class with my wrong method which does not work is below:

import unittest
from article import * /*import my ORM class*/
class EntityTest(unittest.TestCase):
    def setUp(self):
        Entity.db = psycopg2.connect("dbname='postgres' user='postgres' host='192.168.136.129' password='xxxxxxxxx'")/*creates connection to db*/
    def test_should_lounch_attr_error(self):
        article = Article(2)
        print article.title2
        self.assertRaisesRegex(article.AttributeError, "No attribute exists")

I have no expirience how to create test cases and no much good documentation of how to do it((( As I undestood if testcase is passed (exception is generated), unittest should return Ok statement. Now it just shows error.

Upvotes: 0

Views: 441

Answers (1)

mhawke
mhawke

Reputation: 87124

If you do not supply a callable to assertRaisesRegexp() (N.B. assertRaisesRegexp(), not assertRaisesRegex()), then it acts as a context manager. In that case you should use a with statement like this:

import unittest
from article import * /*import my ORM class*/
class EntityTest(unittest.TestCase):
    def setUp(self):
        Entity.db = psycopg2.connect("dbname='postgres' user='postgres' host='192.168.136.129' password='xxxxxxxxx'")/*creates connection to db*/
    def test_should_lounch_attr_error(self):
        with self.assertRaisesRegexp(article.AttributeError, "No attribute exists"):
            article = Article(2)
            print article.title2

Unless your code can raise article.AttributeError with different string representations, I don't think that you actually need to use a regex for this. Just check for article.AttributeError with assertRaises(). This should suffice:

with self.assertRaisesRegexp(article.AttributeError):
    article = Article(2)
    print article.title2

Upvotes: 2

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