test: refactor large event emitter tests

This commit splits several large event emitter tests into smaller
block scoped tests. This keeps the tests more isolated. This
commit also replaces var with const, assert.equal() with
assert.stictEqual(), and other small enhancements.

PR-URL: #6446
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-event-emitter-listeners.js

@@ -1,32 +1,38 @@
 'use strict';
 
 require('../common');
-var assert = require('assert');
-var events = require('events');
+const assert = require('assert');
+const events = require('events');
 
 function listener() {}
 function listener2() {}
 
-var e1 = new events.EventEmitter();
-e1.on('foo', listener);
-var fooListeners = e1.listeners('foo');
-assert.deepStrictEqual(e1.listeners('foo'), [listener]);
-e1.removeAllListeners('foo');
-assert.deepStrictEqual(e1.listeners('foo'), []);
-assert.deepStrictEqual(fooListeners, [listener]);
+{
+  const ee = new events.EventEmitter();
+  ee.on('foo', listener);
+  const fooListeners = ee.listeners('foo');
+  assert.deepStrictEqual(ee.listeners('foo'), [listener]);
+  ee.removeAllListeners('foo');
+  assert.deepStrictEqual(ee.listeners('foo'), []);
+  assert.deepStrictEqual(fooListeners, [listener]);
+}
 
-var e2 = new events.EventEmitter();
-e2.on('foo', listener);
-var e2ListenersCopy = e2.listeners('foo');
-assert.deepStrictEqual(e2ListenersCopy, [listener]);
-assert.deepStrictEqual(e2.listeners('foo'), [listener]);
-e2ListenersCopy.push(listener2);
-assert.deepStrictEqual(e2.listeners('foo'), [listener]);
-assert.deepStrictEqual(e2ListenersCopy, [listener, listener2]);
+{
+  const ee = new events.EventEmitter();
+  ee.on('foo', listener);
+  const eeListenersCopy = ee.listeners('foo');
+  assert.deepStrictEqual(eeListenersCopy, [listener]);
+  assert.deepStrictEqual(ee.listeners('foo'), [listener]);
+  eeListenersCopy.push(listener2);
+  assert.deepStrictEqual(ee.listeners('foo'), [listener]);
+  assert.deepStrictEqual(eeListenersCopy, [listener, listener2]);
+}
 
-var e3 = new events.EventEmitter();
-e3.on('foo', listener);
-var e3ListenersCopy = e3.listeners('foo');
-e3.on('foo', listener2);
-assert.deepStrictEqual(e3.listeners('foo'), [listener, listener2]);
-assert.deepStrictEqual(e3ListenersCopy, [listener]);
+{
+  const ee = new events.EventEmitter();
+  ee.on('foo', listener);
+  const eeListenersCopy = ee.listeners('foo');
+  ee.on('foo', listener2);
+  assert.deepStrictEqual(ee.listeners('foo'), [listener, listener2]);
+  assert.deepStrictEqual(eeListenersCopy, [listener]);
+}

test/parallel/test-event-emitter-remove-all-listeners.js

@@ -1,11 +1,11 @@
 'use strict';
-var common = require('../common');
-var assert = require('assert');
-var events = require('events');
+const common = require('../common');
+const assert = require('assert');
+const events = require('events');
 
 
 function expect(expected) {
-  var actual = [];
+  const actual = [];
   process.on('exit', function() {
     assert.deepStrictEqual(actual.sort(), expected.sort());
   });
@@ -17,56 +17,63 @@ function expect(expected) {
 
 function listener() {}
 
-var e1 = new events.EventEmitter();
-e1.on('foo', listener);
-e1.on('bar', listener);
-e1.on('baz', listener);
-e1.on('baz', listener);
-var fooListeners = e1.listeners('foo');
-var barListeners = e1.listeners('bar');
-var bazListeners = e1.listeners('baz');
-e1.on('removeListener', expect(['bar', 'baz', 'baz']));
-e1.removeAllListeners('bar');
-e1.removeAllListeners('baz');
-assert.deepStrictEqual(e1.listeners('foo'), [listener]);
-assert.deepStrictEqual(e1.listeners('bar'), []);
-assert.deepStrictEqual(e1.listeners('baz'), []);
-// after calling removeAllListeners,
-// the old listeners array should stay unchanged
-assert.deepStrictEqual(fooListeners, [listener]);
-assert.deepStrictEqual(barListeners, [listener]);
-assert.deepStrictEqual(bazListeners, [listener, listener]);
-// after calling removeAllListeners,
-// new listeners arrays are different from the old
-assert.notEqual(e1.listeners('bar'), barListeners);
-assert.notEqual(e1.listeners('baz'), bazListeners);
+{
+  const ee = new events.EventEmitter();
+  ee.on('foo', listener);
+  ee.on('bar', listener);
+  ee.on('baz', listener);
+  ee.on('baz', listener);
+  const fooListeners = ee.listeners('foo');
+  const barListeners = ee.listeners('bar');
+  const bazListeners = ee.listeners('baz');
+  ee.on('removeListener', expect(['bar', 'baz', 'baz']));
+  ee.removeAllListeners('bar');
+  ee.removeAllListeners('baz');
+  assert.deepStrictEqual(ee.listeners('foo'), [listener]);
+  assert.deepStrictEqual(ee.listeners('bar'), []);
+  assert.deepStrictEqual(ee.listeners('baz'), []);
+  // After calling removeAllListeners(),
+  // the old listeners array should stay unchanged.
+  assert.deepStrictEqual(fooListeners, [listener]);
+  assert.deepStrictEqual(barListeners, [listener]);
+  assert.deepStrictEqual(bazListeners, [listener, listener]);
+  // After calling removeAllListeners(),
+  // new listeners arrays is different from the old.
+  assert.notEqual(ee.listeners('bar'), barListeners);
+  assert.notEqual(ee.listeners('baz'), bazListeners);
+}
 
-var e2 = new events.EventEmitter();
-e2.on('foo', listener);
-e2.on('bar', listener);
-// expect LIFO order
-e2.on('removeListener', expect(['foo', 'bar', 'removeListener']));
-e2.on('removeListener', expect(['foo', 'bar']));
-e2.removeAllListeners();
-console.error(e2);
-assert.deepStrictEqual([], e2.listeners('foo'));
-assert.deepStrictEqual([], e2.listeners('bar'));
+{
+  const ee = new events.EventEmitter();
+  ee.on('foo', listener);
+  ee.on('bar', listener);
+  // Expect LIFO order
+  ee.on('removeListener', expect(['foo', 'bar', 'removeListener']));
+  ee.on('removeListener', expect(['foo', 'bar']));
+  ee.removeAllListeners();
+  assert.deepStrictEqual([], ee.listeners('foo'));
+  assert.deepStrictEqual([], ee.listeners('bar'));
+}
 
-var e3 = new events.EventEmitter();
-e3.on('removeListener', listener);
-// check for regression where removeAllListeners throws when
-// there exists a removeListener listener, but there exists
-// no listeners for the provided event type
-assert.doesNotThrow(e3.removeAllListeners.bind(e3, 'foo'));
+{
+  const ee = new events.EventEmitter();
+  ee.on('removeListener', listener);
+  // Check for regression where removeAllListeners() throws when
+  // there exists a 'removeListener' listener, but there exists
+  // no listeners for the provided event type.
+  assert.doesNotThrow(ee.removeAllListeners.bind(ee, 'foo'));
+}
 
-var e4 = new events.EventEmitter();
-var expectLength = 2;
-e4.on('removeListener', function(name, listener) {
-  assert.equal(expectLength--, this.listeners('baz').length);
-});
-e4.on('baz', function() {});
-e4.on('baz', function() {});
-e4.on('baz', function() {});
-assert.equal(e4.listeners('baz').length, expectLength + 1);
-e4.removeAllListeners('baz');
-assert.equal(e4.listeners('baz').length, 0);
+{
+  const ee = new events.EventEmitter();
+  var expectLength = 2;
+  ee.on('removeListener', function(name, listener) {
+    assert.strictEqual(expectLength--, this.listeners('baz').length);
+  });
+  ee.on('baz', function() {});
+  ee.on('baz', function() {});
+  ee.on('baz', function() {});
+  assert.strictEqual(ee.listeners('baz').length, expectLength + 1);
+  ee.removeAllListeners('baz');
+  assert.strictEqual(ee.listeners('baz').length, 0);
+}