Add removeListener() functionality to Event

lib/Event.js

@@ -3,8 +3,9 @@ var sinon = require('sinon');
 module.exports = Event;
 
 function Event() {
-  this.listeners   = [];
-  this.addListener = sinon.spy(this.addListener.bind(this));
+  this.listeners      = [];
+  this.addListener    = sinon.spy(this.addListener.bind(this));
+  this.removeListener = sinon.spy(this.removeListener.bind(this));
 }
 
 /**
@@ -20,6 +21,17 @@ Event.prototype.addListener = function (fn) {
   this.listeners.push(fn);
 };
 
+/**
+ * Remove an event handler function
+ * @param {function} fn
+ */
+Event.prototype.removeListener = function (fn) {
+  var index = this.listeners.indexOf(fn);
+  if (index > -1) {
+    this.listeners.splice(index, 1);
+  }
+};
+
 /**
  * Trigger event
  * @param {...object} arg

test/unit/lib/Event.spec.js

@@ -1,15 +1,16 @@
 var Event = hmt.lib('Event');
 
 describe('Event', function () {
-  var event;
 
-  before(function () {
-    event = new Event();
-  });
 
   describe('addListener', function () {
     var fn;
     var result;
+    var event;
+
+    before(function () {
+      event = new Event();
+    });
 
     before(function () {
       fn = function (name) {
@@ -32,4 +33,42 @@ describe('Event', function () {
       hmt.assert.equal(result, 'hi seth');
     });
   });
+
+  describe('removeListener', function () {
+    var fn;
+    var result;
+    var event;
+
+    before(function () {
+      event = new Event();
+      fn1 = hmt.spy(function Hello (name) {
+        result = 'hi ' + name;
+      });
+
+      fn2 = hmt.spy(function Bye (name) {
+        result = 'goodbye, ' + name;
+      });
+
+      event.addListener(fn2);
+      event.addListener(fn1);
+      event.removeListener(fn1);
+    });
+
+    it('should be a spy', function () {
+      hmt.assert.equal(event.removeListener.callCount, 1);
+    });
+
+    it('should only have recorded the functions that are still being listened to', function () {
+      hmt.assert.equal(event.listeners.length, 1);
+      hmt.assert.equal(event.listeners.indexOf(fn1), -1);
+      hmt.assert.equal(event.listeners.indexOf(fn2) > -1, true);
+    });
+
+    it('should not call the function that is no longer being listened to', function () {
+      event.trigger('mark');
+      hmt.assert.equal(result, 'goodbye, mark');
+      hmt.assert.equal(fn1.callCount, 0);
+      hmt.assert.equal(fn2.callCount, 1);
+    });
+  });
 });