function test_events_stackclick() {
  eventTest_setUpWithMockBlocks();
  var block = workspace.newBlock('field_variable_test_block', '1');
  var events = [
    new Blockly.Events.Ui(block, 'click', undefined, undefined),
    new Blockly.Events.Ui(block, 'stackclick', undefined, undefined)
  ];
  var filteredEvents = Blockly.Events.filter(events, true);
  // click and stackclick should both exist
  assertEquals(2, filteredEvents.length);
  assertEquals('click', filteredEvents[0].element);
  assertEquals('stackclick', filteredEvents[1].element);
  eventTest_tearDownWithMockBlocks();
}
Tests that events that collide on a (event, block, workspace) tuple
but cannot be merged do not get dropped during filtering.