pytest-dash 0.1.3

pytest fixtures to run dash app.

pytest-dash

Pytest fixtures for dash

Install

$ pip install pytest-dash

Fixtures

start_dash

Start a dash instance in a thread, stop the server in teardown.

import dash

import dash_html_components as html

from dash.dependencies import Input, Output
from dash.exceptions import PreventUpdate


def test_app(start_dash, selenium):
    app = dash.Dash(__name__)
    
    app.layout = html.Div([
        html.Div('My test layout', id='out'),
        html.Button('click me', id='click-me')
    ])
    
    @app.callback(Output('out', 'children'), [Input('click-me', 'n_clicks')])
    def on_click(n_clicks):
        if n_clicks is None:
            raise PreventUpdate
        return 'Clicked: {}'.format(n_clicks)
    
    start_dash(app)
    
    btn = selenium.find_element_by_id('click-me')
    btn.click()
    
    out = selenium.find_element_by_id('out')
    assert out.text == 'Clicked: 1'

dash_from_file

Load a file with runpy, return the app instance.

def test_app(dash_from_file):
    app = dash_from_file('usage.py')
    ...

dash_app

Combine start_dash and dash_from_file.

def test_app(dash_app, selenium):
    app = dash_app('usage.py')
    # App has already been started, safe to use selenium from there.
    out = selenium.find_element_by('out')
    ...

More resources

• Dash user guide
• Pytest