Add jobs synchronizer test

[Ngkaokis]

reference site: https://github.com/h2non/gock

[kiootic]

I'm not seeing where the job status is updated?

Also, we can refactor the synchronizer to make it easier to test:

• Extract the webhook server, so that the Synchronizer would accept the two channels instead.
• Extract a Clock interface to make time-based tests faster.

[kiootic]

Can be private function.

[kiootic]

Can use NewNop to avoid polluting output.

[kiootic]

Use jobs_test to avoid using package internal functions.

[Ngkaokis]

if I alter it, I can't create a webhookObject for testing. Should I create another public function sth like NewWebhookObject()

[kiootic]

We should be testing the public interface of the unit, so should use Start instead.

[Ngkaokis]

I'm not seeing where the job status is updated?

Also, we can refactor the synchronizer to make it easier to test:

* Extract the webhook server, so that the Synchronizer would accept the two channels instead.

* Extract a `Clock` interface to make time-based tests faster.

Can you explain more about the Clock interface?

[kiootic]

Can you explain more about the Clock interface?

You can refer here for more details: https://stackoverflow.com/a/18970352

Basically, it would be hard to test time related logic, since 'time' is a global state. To make it easier to test, we uses global time functions through an abstraction, so that we can replace it during testing.

[Ngkaokis]

To alter the package to jobs_test, how to handle the situation that package internal functions/properties are needed (e.g. create webhook object, assert the result)? Should I create getter for those?