test('Debounce Event', function () {
    let doc = new Samples.Document3();

    let onDocDidChange = debounceEvent(doc.onDidChange, (prev: string[], cur) => {
        if (!prev) {
            prev = [cur];
        } else if (prev.indexOf(cur) < 0) {
            prev.push(cur);
        }
        return prev;
    }, 10);

    onDocDidChange(keys => {
        assert.ok(keys, 'was not expecting keys.');
        if (keys.length === 3) {
            doc.setText('4');
            assert.deepEqual(keys, ['1', '2', '3']);
        } else {
            assert.deepEqual(keys, ['4']);
        }
    });

    doc.setText('1');
    doc.setText('2');
    doc.setText('3');
});