Add real unit tests for channel

Before we tested channel implicitly by running it through the tests on
the server.js. After some learning today, it's time to add an own set of
unit tests to channel.

test/channel.js

@@ -0,0 +1,23 @@
+const assert = require('assert');
+const Channel = require("../src/channel.js");
+
+describe('Channel', function () {
+    describe('#contructor()', function () {
+        it("should create a channel", function () {
+            const channel = new Channel("#testchan")
+            assert.equal(typeof channel, 'object')
+        })
+    })
+
+    describe('#join(user)', function () {
+        it("should add the user to a channel and send a JOIN command to the user", function (done) {
+            const channel = new Channel("#testchan")
+            let mockedUser = {nickname: "some_nick"}
+            mockedUser.sendRaw = function(data) {
+                assert.equal(data, ":some_nick JOIN #testchan")
+                done()
+            }
+            channel.join(mockedUser)
+        })
+    })
+})