Server-Side JavaScript with Node.Js - Test-Driven JavaScript Development - page 376

Listing 14.60 Proxying getMessagesSince
chatRoom.waitForMessagesSince = function (id) {
return this.getMessagesSince(id);
};
Now to the interesting part. If the attempt to fetch existing methods does not
succeed, the method should add a listener for the “message” event and go to sleep.
Listing 14.61 tests this by stubbing addListener .
Listing 14.61 Expecting the wait method to add a listener
"should add listener when no messages": function (test) {
this.room.addListener = stub();
var promise = new Promise();
promise.resolve([]);
this.room.getMessagesSince = stub(promise);
this.room.waitForMessagesSince(0);
process.nextTick(function () {
test.equals(this.room.addListener.args[0], "message");
test.isFunction(this.room.addListener.args[1]);
test.done();
}.bind(this));
}
Again we stub the getMessagesSince method to control its output. We
then resolve the promise it's stubbed to return, passing an empty array. This
should cause the waitForMessagesSince method to register a listener for
the “message” event. Seeing as waitForMessagesSince does not add a lis-
tener, the test fails. To pass it, we need to change the implementation as seen in
Listing 14.62.
Listing 14.62 Adding a listener if no messages are available
chatRoom.waitForMessagesSince = function (id) {
var promise = new Promise();
this.getMessagesSince(id).then(function (messages) {
if (messages.length > 0) {
promise.resolve(messages);
} else {
this.addListener("message", function () {});
}