How do I test a callback that returns dash datatable?

Dash Python
1

Hi,

I have created an app that displays a datatable when a button is clicked.
I want to test the callback of this app using dash testing.

What is the correct set for expect?

app.py

from dash import Dash, html, callback, Output, Input, dash_table
import pandas as pd

table_df = pd.DataFrame(
    columns = [f"columns_{i}" for i in range(2)],
    index = [i for i in range(2)]
)

app = Dash(__name__)

app.layout = html.Div([
    html.Button(
        'Run',
        id='run-button',
        n_clicks=0
    ),

    html.Div(
        id="container",
    )
])

@callback(
    Output('container', 'children'),
    Input('run-button', 'n_clicks'),
    prevent_initial_call=True,
)
def show_datatable(n):
    return dash_table.DataTable(table_df.to_dict('records'), [{"name": i, "id": i} for i in table_df.columns])

if __name__ == '__main__':
    app.run_server(debug=True)

test_app.py

import pytest

from app import show_datatable

expect1 = "I am not sure what to put here."

@pytest.mark.parametrize('arg, expect', [
    (1, expect1),
])
def test_show_datatable(arg, expect):
    output = show_datatable(arg)
    assert output == expect