text: // Copyright Joyent, Inc. and other Node contributors.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a
  // copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to permit
  // persons to whom the Software is furnished to do so, subject to the
  // following conditions:
  //
  // The above copyright notice and this permission notice shall be included
  // in all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
  // NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  // USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  module.exports = function (events, assert) {
  
    var callbacks_called = [];
  
    var e = new events.EventEmitter();
  
    function callback1() {
      callbacks_called.push('callback1');
      e.on('foo', callback2);
      e.on('foo', callback3);
      e.removeListener('foo', callback1);
    }
  
    function callback2() {
      callbacks_called.push('callback2');
      e.removeListener('foo', callback2);
    }
  
    function callback3() {
      callbacks_called.push('callback3');
      e.removeListener('foo', callback3);
    }
  
    e.on('foo', callback1);
    assert.equal(1, e.listeners('foo').length);
  
    e.emit('foo');
    assert.equal(2, e.listeners('foo').length);
    assert.deepEqual(['callback1'], callbacks_called);
  
    e.emit('foo');
    assert.equal(0, e.listeners('foo').length);
    assert.deepEqual(['callback1', 'callback2', 'callback3'], callbacks_called);
  
    e.emit('foo');
    assert.equal(0, e.listeners('foo').length);
    assert.deepEqual(['callback1', 'callback2', 'callback3'], callbacks_called);
  
    e.on('foo', callback1);
    e.on('foo', callback2);
    assert.equal(2, e.listeners('foo').length);
    e.removeAllListeners('foo');
    assert.equal(0, e.listeners('foo').length);
  
    // Verify that removing callbacks while in emit allows emits to propagate to
    // all listeners
    callbacks_called = [];
  
    e.on('foo', callback2);
    e.on('foo', callback3);
    assert.equal(2, e.listeners('foo').length);
    e.emit('foo');
    assert.deepEqual(['callback2', 'callback3'], callbacks_called);
    assert.equal(0, e.listeners('foo').length);
  }
  