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.
  
  'use strict';
  const common = require('../common');
  const assert = require('assert');
  const EventEmitter = require('events');
  
  function listener1() {}
  function listener2() {}
  
  {
    const ee = new EventEmitter();
    ee.on('hello', listener1);
    ee.on('removeListener', common.mustCall((name, cb) => {
      assert.strictEqual(name, 'hello');
      assert.strictEqual(cb, listener1);
    }));
    ee.removeListener('hello', listener1);
    assert.deepStrictEqual([], ee.listeners('hello'));
  }
  
  {
    const ee = new EventEmitter();
    ee.on('hello', listener1);
    ee.on('removeListener', common.mustNotCall());
    ee.removeListener('hello', listener2);
    assert.deepStrictEqual([listener1], ee.listeners('hello'));
  }
  
  {
    const ee = new EventEmitter();
    ee.on('hello', listener1);
    ee.on('hello', listener2);
    ee.once('removeListener', common.mustCall((name, cb) => {
      assert.strictEqual(name, 'hello');
      assert.strictEqual(cb, listener1);
      assert.deepStrictEqual([listener2], ee.listeners('hello'));
    }));
    ee.removeListener('hello', listener1);
    assert.deepStrictEqual([listener2], ee.listeners('hello'));
    ee.once('removeListener', common.mustCall((name, cb) => {
      assert.strictEqual(name, 'hello');
      assert.strictEqual(cb, listener2);
      assert.deepStrictEqual([], ee.listeners('hello'));
    }));
    ee.removeListener('hello', listener2);
    assert.deepStrictEqual([], ee.listeners('hello'));
  }
  
  {
    const ee = new EventEmitter();
  
    function remove1() {
      assert.fail('remove1 should not have been called');
    }
  
    function remove2() {
      assert.fail('remove2 should not have been called');
    }
  
    ee.on('removeListener', common.mustCall(function(name, cb) {
      if (cb !== remove1) return;
      this.removeListener('quux', remove2);
      this.emit('quux');
    }, 2));
    ee.on('quux', remove1);
    ee.on('quux', remove2);
    ee.removeListener('quux', remove1);
  }
  
  {
    const ee = new EventEmitter();
    ee.on('hello', listener1);
    ee.on('hello', listener2);
    ee.once('removeListener', common.mustCall((name, cb) => {
      assert.strictEqual(name, 'hello');
      assert.strictEqual(cb, listener1);
      assert.deepStrictEqual([listener2], ee.listeners('hello'));
      ee.once('removeListener', common.mustCall((name, cb) => {
        assert.strictEqual(name, 'hello');
        assert.strictEqual(cb, listener2);
        assert.deepStrictEqual([], ee.listeners('hello'));
      }));
      ee.removeListener('hello', listener2);
      assert.deepStrictEqual([], ee.listeners('hello'));
    }));
    ee.removeListener('hello', listener1);
    assert.deepStrictEqual([], ee.listeners('hello'));
  }
  
  {
    const ee = new EventEmitter();
    const listener3 = common.mustCall(() => {
      ee.removeListener('hello', listener4);
    }, 2);
    const listener4 = common.mustCall();
  
    ee.on('hello', listener3);
    ee.on('hello', listener4);
  
    // listener4 will still be called although it is removed by listener 3.
    ee.emit('hello');
    // This is so because the internal listener array at time of emit
    // was [listener3,listener4]
  
    // Internal listener array [listener3]
    ee.emit('hello');
  }
  
  {
    const ee = new EventEmitter();
  
    ee.once('hello', listener1);
    ee.on('removeListener', common.mustCall((eventName, listener) => {
      assert.strictEqual(eventName, 'hello');
      assert.strictEqual(listener, listener1);
    }));
    ee.emit('hello');
  }
  
  {
    const ee = new EventEmitter();
  
    assert.deepStrictEqual(ee, ee.removeListener('foo', () => {}));
  }
  
  // Verify that the removed listener must be a function
  assert.throws(() => {
    const ee = new EventEmitter();
  
    ee.removeListener('foo', null);
  }, /^TypeError: "listener" argument must be a function$/);
  
  {
    const ee = new EventEmitter();
    const listener = () => {};
    ee._events = undefined;
    const e = ee.removeListener('foo', listener);
    assert.strictEqual(e, ee);
  }
  
  {
    const ee = new EventEmitter();
  
    ee.on('foo', listener1);
    ee.on('foo', listener2);
    assert.deepStrictEqual(ee.listeners('foo'), [listener1, listener2]);
  
    ee.removeListener('foo', listener1);
    assert.strictEqual(ee._events.foo, listener2);
  
    ee.on('foo', listener1);
    assert.deepStrictEqual(ee.listeners('foo'), [listener2, listener1]);
  
    ee.removeListener('foo', listener1);
    assert.strictEqual(ee._events.foo, listener2);
  }
  