Allow users to define ordering for TestNG listeners

[krmahadevan]

On a high level here's the requirements that we can start off with to decide on the implementation details of #2874

• User defines a comparator that basically takes in two listener objects (implementations of ITestNGListener)
• Using the comparator the user determines the execution order.
• User plugs in this comparator as a configuration.
• TestNG uses this new comparator to determine order and reverse-order for listeners.

The last portion that needs to be vetted out is to decide if we should include IReporter implementations.

Our IReporter api by its design is allowing users to alter the state of the ITestResult object (we dont enforce READ-ONLY)

[juherr]

Thanks for taking the lead on the feature @krmahadevan 👍

My points:

• If TestNG must instantiate the comparator, what are the constraints/limitations on the constructor?
• What is the definition of the default order?
• User plugs in this comparator as a configuration -> Could you precise your mind?
• I vote to exclude IReporter from the feature because it will be more difficult to remove it later if it is a bad idea (but could be easily added if we found a true use case)

[juherr]

It looks good.

Why not start by the documentation? We will be able to use it as a specification.

[krmahadevan]

Why not start by the documentation? We will be able to use it as a specification.

You mean, by creating a PR for https://github.com/testng-team/testng-team.github.io that explains how to use this feature?

[juherr]

Yes, exactly! WDYT?

[krmahadevan]

Sure. Let me work on getting that done over the weekend.

[krmahadevan]

@juherr - Please check this PR testng-team/testng-team.github.io#74