How to supply stdin, files and environment variable inputs to Python unit tests?

Question

How to write tests where conditions like the following arise:

1. Test user Input.
2. Test input read from a file.
3. Test input read from an environme

Answer 1

Using pytest:

import os


def test_user_input(monkeypatch):
    inputs = [10, 'y']
    input_generator = (i for i in inputs)
    monkeypatch.setattr('__builtin__.raw_input', lambda prompt: next(input_generator))
    assert raw_input('how many?') == 10
    assert raw_input('you sure?') == 'y'


def test_file_input(tmpdir):
    fixture = tmpdir.join('fixture.txt')
    fixture.write(os.linesep.join(['1', '2', '3']))
    fixture_path = str(fixture.realpath())
    with open(fixture_path) as f:
        assert f.readline() == '1' + os.linesep


def test_environment_input(monkeypatch):
    monkeypatch.setenv('STAGING', 1)
    assert os.environ['STAGING'] == '1'