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test: refactor event-emitter-remove-all-listeners #13165

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test: refactor event-emitter-remove-all-listeners #13165

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29 changes: 15 additions & 14 deletions test/parallel/test-event-emitter-remove-all-listeners.js
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Original file line number Diff line number Diff line change
Expand Up @@ -38,24 +38,25 @@ function expect(expected) {

{
const ee = new events.EventEmitter();
ee.on('foo', common.noop);
ee.on('bar', common.noop);
ee.on('baz', common.noop);
ee.on('baz', common.noop);
const noop = common.mustNotCall();
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Why not bring this up to the parent scope and use it in the other places below that are now manually calling common.mustNotCall()?

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+1
But give it a better name... maybe mustNotCall or if your thight with char dontCall or even doNot

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@Trott Trott May 23, 2017 •
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Why not bring this up to the parent scope and use it in the other places below that are now manually calling common.mustNotCall()?

@mscdex Happy to do that if there's consensus that it would be an improvement. I didn't do it because:

  • It's not needed as an identifier in the other scopes. (It's needed here because of the assert.deepStrictEqual() comparisons.)

  • Fewer global identifiers shared across different block scopes helps make those things easily cut-and-paste-able into separate test files for refactoring, etc. It also helps limit the possibility of side effects. (For example, if another test attaches a property to the noop function for some reason, that property will be set for all the other tests.)

But this isn't far off from a tabs-vs-spaces discussion, so I'm happy to just do it if everyone else thinks differently than me. :-D

ee.on('foo', noop);
ee.on('bar', noop);
ee.on('baz', noop);
ee.on('baz', noop);
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'), [common.noop]);
assert.deepStrictEqual(ee.listeners('foo'), [noop]);
assert.deepStrictEqual(ee.listeners('bar'), []);
assert.deepStrictEqual(ee.listeners('baz'), []);
// After calling removeAllListeners(),
// the old listeners array should stay unchanged.
assert.deepStrictEqual(fooListeners, [common.noop]);
assert.deepStrictEqual(barListeners, [common.noop]);
assert.deepStrictEqual(bazListeners, [common.noop, common.noop]);
assert.deepStrictEqual(fooListeners, [noop]);
assert.deepStrictEqual(barListeners, [noop]);
assert.deepStrictEqual(bazListeners, [noop, noop]);
// After calling removeAllListeners(),
// new listeners arrays is different from the old.
assert.notStrictEqual(ee.listeners('bar'), barListeners);
Expand All @@ -64,8 +65,8 @@ function expect(expected) {

{
const ee = new events.EventEmitter();
ee.on('foo', common.noop);
ee.on('bar', common.noop);
ee.on('foo', common.mustNotCall());
ee.on('bar', common.mustNotCall());
// Expect LIFO order
ee.on('removeListener', expect(['foo', 'bar', 'removeListener']));
ee.on('removeListener', expect(['foo', 'bar']));
Expand All @@ -76,7 +77,7 @@ function expect(expected) {

{
const ee = new events.EventEmitter();
ee.on('removeListener', common.noop);
ee.on('removeListener', common.mustNotCall());
// Check for regression where removeAllListeners() throws when
// there exists a 'removeListener' listener, but there exists
// no listeners for the provided event type.
Expand All @@ -89,9 +90,9 @@ function expect(expected) {
ee.on('removeListener', function(name, noop) {
assert.strictEqual(expectLength--, this.listeners('baz').length);
});
ee.on('baz', common.noop);
ee.on('baz', common.noop);
ee.on('baz', common.noop);
ee.on('baz', common.mustNotCall());
ee.on('baz', common.mustNotCall());
ee.on('baz', common.mustNotCall());
assert.strictEqual(ee.listeners('baz').length, expectLength + 1);
ee.removeAllListeners('baz');
assert.strictEqual(ee.listeners('baz').length, 0);
Expand Down