python click + pytest example

split_into_2_files.py

# hello.py
import click

@click.command()
@click.option(
    '--name', default='world',
    prompt='greet whom?',
    help='who should i greet?'
)
def main(name):
    click.echo('Hello {}!'.format(name))

# test_hello.py
from click.testing import CliRunner
import pytest

from hello import hello as hll


@pytest.fixture(scope="module")
def runner():
    return CliRunner()

def test_named_hello(runner):
    result = runner.invoke(hll.main, ['--name','Amy'])
    assert result.exit_code == 0
    assert result.output == 'Hello Amy!\n'


def test_default_hello(runner):
    result = runner.invoke(hll.main, input='\n')
    assert result.exit_code == 0
    print(result.output)
    expected = 'greet whom? [world]: \nHello world!\n'
    assert result.output == expected

Note: it would be better to add the following code after result = runner.invoke(...

if result.exception:
    traceback.print_exception(*result.exc_info)

It took me a while to figure out the exception was "trapped" by clirunner.

@dtranhuusm you're a life saver :) Thank You!!

There is now a flag, which says to trap catch or not exceptions

  result = cli_runner.invoke(
      cli,
      catch_exceptions=False,
      args=[],
  )