Testing argument using Python Click

Question

I have a command-line script with Python-click with an argument and option:

# console.py
import click

@click.command()
@click.version_option()
@click.argument("filepath", type=click.Path(exists=True), default=".")
@click.option(
    "-m",
    "--max-size",
    type=int,
    help="Max size in megabytes.",
    default=20,
    show_default=True,
)
def main(filepath: str, max_size: int) -> None:
    max_size_bytes = max_size * 1024 * 1024  # convert to MB
    if filepath.endswith(".pdf"):
        print("success")
    else:
        print(max_size_bytes)

Both the argument and option have default values and work on the command-line and using the CLI it behaves as expected. But when I try testing it following Click documentation and debug it, it does not enter the first line:

# test_console.py
from unittest.mock import Mock

import click.testing
import pytest
from pytest_mock import MockFixture

from pdf_split_tool import console

@pytest.fixture
def runner() -> click.testing.CliRunner:
    """Fixture for invoking command-line interfaces."""
    return click.testing.CliRunner()

@pytest.fixture
def mock_pdf_splitter_pdfsplitter(mocker: MockFixture) -> Mock:
    """Fixture for mocking pdf_splitter.PdfSplitter."""
    return mocker.patch("pdf_split_tool.pdf_splitter.PdfSplitter", autospec=True)

def test_main_uses_specified_filepath(
    runner: click.testing.CliRunner,
    mock_pdf_splitter_pdfsplitter: Mock, 
) -> None:
    """It uses the specified filepath."""
    result = runner.invoke(console.main, ["test.pdf"])
    assert result.exit_code == 0

I couldn't see why it is giving since the debugger did not enter the first line of function main(). Any ideas of what could be wrong?

I've been using click's testing package for a while, but it has caused me bugs and grief and I switched to invoking my entry points myself. You might want to do the same — kmaork
– kmaork, Commented Jun 4, 2020 at 21:34

codeforester · Accepted Answer · 2025-04-25 22:38:26Z

7

+50

The failure is due to following error.

(pdb)print result.output
"Usage: main [OPTIONS] [FILEPATH]\nTry 'main --help' for help.\n\nError: Invalid value for '[FILEPATH]': Path 'test.pdf' does not exist.\n"

This is happening due to following code in console.py which checks if the filepath exists. @click.argument("filepath", type=click.Path(exists=True), default=".")

One way to test creating a temporary file is using afterburner's code:

# test_console.py
def test_main_uses_specified_filepath() -> None:
    runner = click.testing.CliRunner()
    with runner.isolated_filesystem():
        with open('test.pdf', 'w') as f:
            f.write('Hello World!')

        result = runner.invoke(main, ["test.pdf"])
    assert result.exit_code == 0

edited Apr 25 at 22:38

codeforester

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answered Jun 2, 2020 at 16:43

apoorva kamath

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1 Comment

staticdev Over a year ago

Thanks apoorva kamath! How can I see this error? afterburner just posted a test code as a complement to your answer. If you just could complete your answer with the code (since the bounty specified it needed code) I will mark as the right answer.

afterburner · Accepted Answer · 2020-06-02 18:16:52Z

5

I've changed your test method to the following. However, this is more an augmentation to apoorva kamath's answer.


def test_main_uses_specified_filepath() -> None:
    runner = click.testing.CliRunner()
    with runner.isolated_filesystem():
        with open('test.pdf', 'w') as f:
            f.write('Hello World!')

        result = runner.invoke(main, ["test.pdf"])
    assert result.exit_code == 0

Simply put, it creates an isolated file system that gets cleaned up after the text is executed. So any files created there are destroyed with it.

For more information, Click's Isolated Filesystem documentation might come in handy.

Alternatively, you can remove the exists=True parameter to your file path.

edited Jun 2, 2020 at 18:16

answered Jun 2, 2020 at 18:10

afterburner

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4 Comments

staticdev Over a year ago

Thanks @afterburner. I think the answer is a merge of both your answers. Since apoorva kamath answered first I will give the right answer to her (and an upvote for you).

afterburner Over a year ago

@staticdev appreciate it, and I approve, she's the one that figured it out

staticdev Over a year ago

Just a minor improvement, as f and the f.write are not necessary to work. You can put the invoke in the place of f.write instead. =p

afterburner Over a year ago

True. I wasn't sure if Python created an empty file if nothing was written to it, but today I learnt :D

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