Evented Node.js EventEmitter compatibility guarantees

test/event/EventableTest.js

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+/**
+ * Tests 1-N message dispatch interface
+ *
+ *  Copyright (C) 2014 Mike Gerwitz
+ *
+ *  This file is part of jsTonic.
+ *
+ *  jstonic is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+var Sut    = require( '../../' ).event.Eventable,
+    expect = require( 'chai' ).expect;
+
+
+describe( 'event.Eventable', () =>
+{
+    /**
+     * One critical design decision of Eventable was to produce an interface
+     * that is compatible with Node.js' EventEmitter prototype---this allows
+     * existing Node libraries that make use of it to be used wherever an
+     * Eventable is expected, without any frustrating adapter code that
+     * would deter developers.
+     *
+     * Note an important distinction here: Eventable defines a *subset* of
+     * the methods implemented by EventEmitter; so implementors of Eventable
+     * may provide other methods in addition, and EventEmitter likewise does
+     * the same; the only goal we care about is that EventEmitter can be
+     * used polymorphically with regards to Eventable. Therefore, while it's
+     * true that EventEmitter can be used wherever Eventable is expected,
+     * the reverse is not necessarily true.
+     *
+     * This test was created when the Event interface had already been
+     * declared "frozen", so the below methods should be correct.
+     */
+    it( 'is compatible with Node.js Event prototype', () =>
+    {
+        let f = ( ev, listener ) => {};
+
+        let njs_ev = {
+            addListener:        f,
+            on:                 f,
+            once:               f,
+            removeListener:     f,
+            removeAllListeners: f,
+            setMaxListeners:    f,
+            listeners:          f,
+            emit:               f,
+        };
+
+        // via ease.js ECMAScript interop
+        expect( Sut.isCompatible( njs_ev ) ).to.be.true;
+    } );
+} );
+