test: exercise once() with varying arguments

This commit regains test coverage for EventEmitter#once() with four or more arguments. To avoid similar regressions in the future, once() is called with enough arguments to cover all of the separate code paths. PR-URL: #13524 Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com> Reviewed-By: James M Snell <jasnell@gmail.com>

Author: cjihrig

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

@@ -55,3 +55,23 @@ assert.throws(() => {
 
  ee.once('foo', null);
 }, /^TypeError: "listener" argument must be a function$/);
+
+{
+ // once() has different code paths based on the number of arguments being
+ // emitted. Verify that all of the cases are covered.
+ const maxArgs = 4;
+
+ for (let i = 0; i <= maxArgs; ++i) {
+ const ee = new EventEmitter();
+ const args = ['foo'];
+
+ for (let j = 0; j < i; ++j)
+ args.push(j);
+
+ ee.once('foo', common.mustCall((...params) => {
+ assert.deepStrictEqual(params, args.slice(1));
+ }));
+
+ EventEmitter.prototype.emit.apply(ee, args);
+ }
+}