button.fireEvent('click', button);

1)Create the event code in a function and call the function from both sides: btn.on("clic", ...) and from the code you want to simulate the click.

2)Use: btnView.btnEl.dom.click();

Ext.create('Ext.Button', {
    text: 'Click me',
    renderTo: Ext.getBody(),
    handler: function() {
        alert('You clicked the button!');
    }
});

Ext.create('Ext.Button', {
    text: 'Click me',
    renderTo: Ext.getBody(),
    handler: someOnClickFunction
});

someOnClickFunction = function( aButton, aEvent, aeOpts)
{
    // Do something here
}