An example how you can test DevExpress ASP controls with TestCafe

test.js

import { Selector } from 'testcafe';

fixture `DX Controls`
    .page `https://demos.devexpress.com/aspxgridviewdemos/GridEditing/EditModes.aspx`;

const ComboBox = class {
    constructor (id) {
        this.id = id;
        
        this.dropDownBtn = Selector(`#${id}_B-1`);
        this.popup = Selector(`#${id}_DDD_PW-1`);
    }

    getItem (text) {
        return this.popup.find('td[class^="dxeListBoxItem"]').withText(text)
    }
}

const Grid = class {
    constructor(id) {
        this.id = id;
        this.mainElement = Selector(`#${id}`);
    }

    getRow (idx) {
        return Selector(`#${this.id}_DXDataRow${idx}`);
    }

    getEditingRow () {
        return Selector(`#${this.id}_DXEditingRow`);
    }

    getEditBtn (rowIdx) {
        return this.getRow(rowIdx).find('span').withText('Edit');
    }

    getUpdateBtn (rowIdx) {
        return this.getEditingRow().find('span').withText('Update');
    }

    getEditor (columnIdx) {
        return Selector(`#${this.id}_DXEditor${columnIdx}_I`);
    }

    getCell (rowIdx, columnIdx) {
        return Selector(`#${this.id}_DXMainTable`).find('tr[class^="dxgvDataRow"]').nth(rowIdx).find('td').nth(columnIdx);
    }
}

test('test1', async t => {
    const grid = new Grid('ContentHolder_grid');
    const combobox = new ComboBox('ControlOptionsTopHolder_ddlEditMode')

    await t
        .click(combobox.dropDownBtn)
        .click(combobox.getItem('Inline'))
        .click(grid.getEditBtn(0))
        .typeText(grid.getEditor(1), 'My Name', { replace: true })
        .click(grid.getUpdateBtn(0))
        .expect(grid.getCell(0, 1).textContent).eql('My Name');
});