For loop in unittest

Question

Is there a way to tell the python unittest execute all assertion in a method and show all cases it fails, instead of stop at the first failed.

class MyTestCase(TestCase):
    def test_a(self):
        with open('testcase.txt') as ifile: 
            for iline in ifile:
                self.assertEqual(iline, 'it is a test!')

Answer 1

Python 3.4 introduced the subTest context manager. Your code will look like

class MyTestCase(TestCase):
    def test_a(self):
        with open('testcase.txt') as ifile: 
            for iline in ifile:
                with self.subTest(line=iline):
                    self.assertEqual(iline, 'it is a test!')

The ugly way to achieve this without subTest is to make self.assert* calls within a try block, print the errors caught, and raise the AssertionError explicitly after the loop if at least one test failed.

Answer 2

Alternatively, you can make a data-driven-test with the help of ddt package:

DDT (Data-Driven Tests) allows you to multiply one test case by running it with different test data, and make it appear as multiple test cases.

import unittest
from ddt import ddt, data

@ddt
class FooTestCase(unittest.TestCase):
    @data('it is a test!', 'it is a test!', 'something else')
    def test_lines(self, value):
        self.assertEqual(value, 'it is a test!')

ddt can also have the data coming from a file, but it has to be a JSON file.