Python Language Unit Testing Unit tests with pytest
Example
installing pytest:
pip install pytest
getting the tests ready:
mkdir tests
touch tests/test_docker.py
Functions to test in docker_something/helpers.py:
from subprocess import Popen, PIPE
# this Popen is monkeypatched with the fixture `all_popens`
def copy_file_to_docker(src, dest):
try:
result = Popen(['docker','cp', src, 'something_cont:{}'.format(dest)], stdout=PIPE, stderr=PIPE)
err = result.stderr.read()
if err:
raise Exception(err)
except Exception as e:
print(e)
return result
def docker_exec_something(something_file_string):
fl = Popen(["docker", "exec", "-i", "something_cont", "something"], stdin=PIPE, stdout=PIPE, stderr=PIPE)
fl.stdin.write(something_file_string)
fl.stdin.close()
err = fl.stderr.read()
fl.stderr.close()
if err:
print(err)
exit()
result = fl.stdout.read()
print(result)
The test imports test_docker.py:
import os
from tempfile import NamedTemporaryFile
import pytest
from subprocess import Popen, PIPE
from docker_something import helpers
copy_file_to_docker = helpers.copy_file_to_docker
docker_exec_something = helpers.docker_exec_something
mocking a file like object in test_docker.py:
class MockBytes():
'''Used to collect bytes
'''
all_read = []
all_write = []
all_close = []
def read(self, *args, **kwargs):
# print('read', args, kwargs, dir(self))
self.all_read.append((self, args, kwargs))
def write(self, *args, **kwargs):
# print('wrote', args, kwargs)
self.all_write.append((self, args, kwargs))
def close(self, *args, **kwargs):
# print('closed', self, args, kwargs)
self.all_close.append((self, args, kwargs))
def get_all_mock_bytes(self):
return self.all_read, self.all_write, self.all_close
Monkey patching with pytest in test_docker.py:
@pytest.fixture
def all_popens(monkeypatch):
'''This fixture overrides / mocks the builtin Popen
and replaces stdin, stdout, stderr with a MockBytes object
note: monkeypatch is magically imported
'''
all_popens = []
class MockPopen(object):
def __init__(self, args, stdout=None, stdin=None, stderr=None):
all_popens.append(self)
self.args = args
self.byte_collection = MockBytes()
self.stdin = self.byte_collection
self.stdout = self.byte_collection
self.stderr = self.byte_collection
pass
monkeypatch.setattr(helpers, 'Popen', MockPopen)
return all_popens
Example tests, must start with the prefix test_ in the test_docker.py file:
def test_docker_install():
p = Popen(['which', 'docker'], stdout=PIPE, stderr=PIPE)
result = p.stdout.read()
assert 'bin/docker' in result
def test_copy_file_to_docker(all_popens):
result = copy_file_to_docker('asdf', 'asdf')
collected_popen = all_popens.pop()
mock_read, mock_write, mock_close = collected_popen.byte_collection.get_all_mock_bytes()
assert mock_read
assert result.args == ['docker', 'cp', 'asdf', 'something_cont:asdf']
def test_docker_exec_something(all_popens):
docker_exec_something(something_file_string)
collected_popen = all_popens.pop()
mock_read, mock_write, mock_close = collected_popen.byte_collection.get_all_mock_bytes()
assert len(mock_read) == 3
something_template_stdin = mock_write[0][1][0]
these = [os.environ['USER'], os.environ['password_prod'], 'table_name_here', 'test_vdm', 'col_a', 'col_b', '/tmp/test.tsv']
assert all([x in something_template_stdin for x in these])
running the tests one at a time:
py.test -k test_docker_install tests
py.test -k test_copy_file_to_docker tests
py.test -k test_docker_exec_something tests
running all the tests in the tests folder:
py.test -k test_ tests
