Unit tests for progress bar in pytest

[EdLeafe]

I have been working on adding rich to my CLI application by wrapping calls to rich in my output classes, and am writing unit tests to verify that it is working correctly. I use pytest as my testing framework, and use the capsys fixture for capturing and evaluating output. So far it's been great, but now I'm trying to unit test the progress bar code, and nothing is showing up in the captured output. I have verified that if I remove capsys, the progress bar is correctly written to the screen, but that is useless for testing.

To rule out that it was something in my wrappers that was the issue, I created some very simple unit tests: one with capsys, one with capsysbinary, and one with no capture just to demonstrate that it does actually write to the terminal output.

Can anyone help explain what I need to do to properly capture the output from the progress bar? Oh, I also tried creating a Console with record=True, and then checking the value from export_text(), but it's always empty, too.

import time

import pytest
from rich.console import Console
from rich.progress import BarColumn, Progress

TOTAL = 30
STEP = 5
LABEL = "Processing..."


def test_progress_bar(capsys):
    console = Console()
    progress = Progress(
        "[progress.description]{task.description}",
        BarColumn(),
        "[magenta]{task.completed} of {task.total} completed",
        console=console,
    )
    curr = 0
    with progress:
        task = progress.add_task(LABEL, total=TOTAL)
        while curr < TOTAL:
            curr += STEP
            time.sleep(0.1)
            progress.update(task, advance=STEP)
    cap = capsys.readouterr()
    assert LABEL in cap.out


def test_progress_bar_binary(capsysbinary):
    console = Console()
    progress = Progress(
        "[progress.description]{task.description}",
        BarColumn(),
        "[magenta]{task.completed} of {task.total} completed",
        console=console,
    )
    curr = 0
    with progress:
        task = progress.add_task(LABEL, total=TOTAL)
        while curr < TOTAL:
            curr += STEP
            time.sleep(0.1)
            progress.update(task, advance=STEP)
    cap = capsysbinary.readouterr()
    assert LABEL in cap.out.decode()


def test_progress_bar_no_capsys():
    console = Console()
    progress = Progress(
        "[progress.description]{task.description}",
        BarColumn(),
        "[magenta]{task.completed} of {task.total} completed",
        console=console,
    )
    curr = 0
    with progress:
        task = progress.add_task(LABEL, total=TOTAL)
        while curr < TOTAL:
            curr += STEP
            time.sleep(0.1)
            progress.update(task, advance=STEP)
    # Can't assert anything, since we haven't captured the output.
    # But you can see it in the terminal when you run the test.
    assert True

[willmcgugan]

Hi Ed,

I think I know what is going on. Rich will hide things like progress bars if it detects it is not writing to a terminal. This is because you don't want all the frames of progress bars written out if you are piping to a file for example.

You can add force_terminal=True to the Console constructor to bypass that and render the progress bars.

[EdLeafe]

That did it! Thanks for the quick response!