Testing click with logging or return values instead of print

Question

When I test click, I understand the basic setup looks something like this:

import click

@click.command()
@click.argument('name')
def hello(name):
   click.echo('Hello %s!' % name)

Test file

from click.testing import CliRunner
from hello import hello

def test_hello_world():
  runner = CliRunner()
  result = runner.invoke(hello, ['Peter'])
  assert result.exit_code == 0
  assert result.output == 'Hello Peter!\n'

However, if I use logging instead of print, I can't capture the output or check the return value of a command. For example:

import click
import logging as log

@click.command()
@click.argument('name')
def hello(name):
   log.info('Hello %s!' % name)
   return name

I can't check to see if that return value is correct without printing or click.echo'ing it.

Is there a way to check for return values or check output against logging using click?

Stephen Rauch · Accepted Answer · 2021-02-22 14:52:27Z

7

You can use the caplog fixture in pytest to capture the logging output like this:

def test_hello_world(caplog):
  runner = CliRunner()
  result = runner.invoke(hello, ['Peter'])
  assert result.exit_code == 0
  assert result.output == ''
  assert caplog.messages == ['Hello Peter!']

As for wanting to check the "return" value of the command handler, Click decorated commands do not return anything in the conventional sense. The command itself uses the system return value, which is being tested here on the result.exit_code.

If you really think you need to use the return value from the command handler, you can set the stand_alone flag.

edited Feb 22, 2021 at 14:52

answered Feb 21, 2021 at 16:32

Stephen Rauch♦

50.1k32 gold badges118 silver badges143 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Cristiano Over a year ago

what if an exception is raised while executing the internal command? how can click capture that and pass to pytest to fail the test?

Stephen Rauch Over a year ago

@Cristiano stackoverflow.com/a/65394602/7311767

Collectives™ on Stack Overflow

Testing click with logging or return values instead of print

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related