pytest-textual-snapshot

Snapshot testing for Textual apps.

Installation

Install using pip:

pip install pytest-textual-snapshot

After installing, the snap_compare fixture will automatically be made available.

About

A pytest-textual-snapshot test saves an SVG screenshot of a running Textual app to disk. The next time the test runs, it takes another screenshot and compares it to the saved one. If the new screenshot differs from the old one, the test fails. This is a convenient way to quickly and automatically detect visual regressions in your applications.

Usage

Running tests

You can run your tests using pytest as normal.

My snapshot test failed, what do I do?

If your snapshot test fails, it means that the screenshot taken during the test session differs from the last screenshot taken. This change is shown in the failure report, which you'll be given a linked to in the event of a failure.

If the diff shown in the failure report looks correct, you can update the snapshot on disk by running pytest with the --snapshot-update flag.

Writing tests

Basic usage

Inject the snap_compare fixture into your test and call it with the path to the Textual app (the file containing the App subclass).

def test_something(snap_compare):
    assert snap_compare("path/to/app.py")

Pressing keys

Key presses can be simulated before the screenshot is taken.

def test_something(snap_compare):
    assert snap_compare("path/to/app.py", press=["tab", "left", "a"])