Tests pass on local instance and fail on repo instance

Problem/Motivation

I posted this support request to get some help from the experts in understanding how to debug Drupal's automated tests, based upon what I perceived as erratic behaviour from some automated tests I had written some tests for my project Anonymous Publishing.

[Background: For local testing, I navigate to Administration » Configuration » Development » Testing, check the box for the module I want to test, and press "Run tests". For testing on Drupal.org, I queue a test using the project page "Automated testing" tab.]

When I run the tests on a local test instance, I get the result: "214 passes, 0 fails, 0 exceptions, and 99 debug messages".
When I run the tests on the same version using the Drupal.org test instance, I get: "10 pass, 5 fail".

Not only are the numbers different, but test cases that pass on the local test instance fail when run on Drupal.org.

I initially had no idea about how to go about debugging this, hence this cry for help.

After using a copious amount of debug statements I finally discovered that the URLs appearing in my local test instance looked like this:

http://EXAMPLE.ORG/node/2/verify?akey=SOME-ACTIVATION-KEY

While those produced by the Drupal.org test instance looked like this.

http://localhost/checkout/?q=node/2/verify&akey=SOME-ACTIVATION-KEY

So it turns that there was a problem with my code after all. My too-crude URL parsing assumes "clean URLs" and do not work on a site that uses the ?q= construct to indicate the path to a node.

(So Hurrah! for automated testing.)

Proposed resolution

Fix module being tested so that URL-parsing works whether clean URLs are enabled or not.

Remaining tasks

None (closing issue).