Hmmm....interesting question. I would believe so because if you inspect the element, the property in the html is 'data-qtip,' which directly correlates to the values of the tagConfig property that is defined in Ext.tip.QuickTip. Secondly, if you hover the mouse over the button while the test is running so that the tip pops up, then the test will continue and pass.
StartTest(function (t) {
var Ext = t.getExt();
var cmp = Ext.create('Ext.button.Button', {
renderTo: Ext.getBody(),
text: 'Some Button',
tooltip: 'A tooltip describes the purpose'
});
var M = Ext.tip.QuickTipManager;
M.init();
t.moveMouseTo(cmp.el);
t.waitForComponentVisible(M.getQuickTip(), function () {
t.pass('Tooltip was displayed');
});
});