test_integration.py

from multiprocessing import Value
import dash_html_components as html
import dash_core_components as dcc
from dash import Dash
from dash.dependencies import Input, Output
from .IntegrationTests import IntegrationTests
from .utils import assert_clean_console, invincible, wait_for


class Tests(IntegrationTests):
    def setUp(self):
        def wait_for_element_by_id(id):
            wait_for(lambda: None is not invincible(
                lambda: self.driver.find_element_by_id(id)
            ))
            return self.driver.find_element_by_id(id)
        self.wait_for_element_by_id = wait_for_element_by_id

    def test_simple_callback(self):
        app = Dash(__name__)
        app.layout = html.Div([
            dcc.Input(
                id='input',
                value='initial value'
            ),
            html.Div(
                html.Div([
                    1.5,
                    None,
                    'string',
                    html.Div(id='output-1')
                ])
            )
        ])

        call_count = Value('i', 0)

        @app.callback(Output('output-1', 'children'), [Input('input', 'value')])
        def update_output(value):
            call_count.value = call_count.value + 1
            return value

        self.startServer(app)

        output1 = self.wait_for_element_by_id('output-1')
        wait_for(lambda: output1.text == 'initial value')
        self.percy_snapshot(name='simple-callback-1')

        input1 = self.wait_for_element_by_id('input')
        input1.clear()

        input1.send_keys('hello world')

        output1 = lambda: self.wait_for_element_by_id('output-1')
        wait_for(lambda: output1().text == 'hello world')
        self.percy_snapshot(name='simple-callback-2')

        self.assertEqual(
            call_count.value,
            # an initial call to retrieve the first value
            1 +
            # one for each hello world character
            len('hello world')
        )

        assert_clean_console(self)