Pytest: Mocking STDIN - monkeypatch

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examples/pytest/stdin/test_both_monkeypatch.py

import app
import io
import sys

def test_one(capsys, monkeypatch):
    monkeypatch.setattr(sys, 'stdin', io.StringIO('Foo'))
    app.ask_one()
    out, err = capsys.readouterr()
    assert err == ''
    #print(out)
    assert out == 'Please enter your name: Your name is Foo\n'

def test_two(monkeypatch, capsys):
    monkeypatch.setattr(sys, 'stdin', io.StringIO('3\n4'))
    app.ask_two()
    out, err = capsys.readouterr()
    assert err == ''
    #print(out)
    assert out == 'Please enter width: Please enter length: 3.0*4.0 is 12.0\n'