function test_events_filteraftermerge() {
  eventTest_setUpWithMockBlocks();
  var block = workspace.newBlock('field_variable_test_block', '1');
  block.setParent(null);
  var events = [];
  helper_addMoveEventParent(events, block, null);
  helper_addMoveEventParent(events, block, null);
  var filteredEvents = Blockly.Events.filter(events, true);
  // The two events should be merged, but because nothing has changed
  // they will be filtered out.
  assertEquals(0, filteredEvents.length);
  eventTest_tearDownWithMockBlocks();
}
Mutator composition could result in move events for blocks
connected to the mutated block that were null operations. This
leads to events in the undo/redo queue that do nothing, requiring
an extra undo/redo to proceed to the next event. This test ensures
that two move events that do get merged (disconnecting and
reconnecting a block in response to a mutator change) are filtered
from the queue.