Unit Test Notes

Unit.md

unittest — Unit testing framework

The Python unit testing framework, sometimes referred to as “PyUnit”.

unittest supports test automation, sharing of setup and shutdown code for tests, aggregation of tests into collections, and independence of the tests from the reporting framework. The unittest module provides classes that make it easy to support these qualities for a set of tests.

To achieve this, unittest supports some important concepts:

• test fixture
  • A test fixture represents the preparation needed to perform one or more tests, and any associate cleanup actions. This may involve, for example, creating temporary or proxy databases, directories, or starting a server process.
• test case
  • A test case is the smallest unit of testing. It checks for a specific response to a particular set of inputs. unittest provides a base class, TestCase, which may be used to create new test cases.
• test suite
  • A test suite is a collection of test cases, test suites, or both. It is used to aggregate tests that should be executed together.
• test runner
  • A test runner is a component which orchestrates the execution of tests and provides the outcome to the user. The runner may use a graphical interface, a textual interface, or return a special value to indicate the results of executing the tests.

The standard workflow is:

1. You define your own class derived from unittest.TestCase.
2. Then you fill it with functions that start with test_.
3. You run the tests by placing unittest.main() in your file, usually at the bottom.

Example: test_unittest.py

import unittest
class TestUM(unittest.TestCase):
    def setUp(self):
        pass

    def test_example(self):
        self.assertEqual(true, true)

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

Running unittests:

$ python test_unittest.py

Ref:

• unittest introduction
• unittest — Unit testing framework

Coverage Report:

pip install pytest-cov
py.test --cov .

mock:

import mock
import unittest

from Project.package import object_a

class SomeTestCase(unittest.TestCase):
    # the same: @mock.patch.object(object_a, 'method_a')
    @mock.patch("Project.package.object_a.method_a")
    def test_some_test(self, mock_function_a):
       mock_function_a.return_value = "return_value"

monkeypatching:

from Project.package import object_a

def mock_method_a(name)
    return name

def test_some_test(monkeypatch):
    monkeypatch.setattr(object_a, 'method_a', mock_method_a)

monkeypatching in class, notice that this is only valid for "standard" pytest classes (not unittest.TestCase subclasses).:

class Test:
    def setup_calss(self):
        pass
    def teardown_class(self):
       pass
    def test_some_function(self, monkeypatch):
       pass

Mock python builtin functions in pytest:

import __builtin__
...
monkeypatch.setattr(__builtin__, 'raw_input', mock_raw_input)

Asserting that a certain exception is raised in pytest:

import pytest
with pytest.raises(Exception):
    f()

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