Definition of Done must include Testing ?

Is the increment potentially reléase releasable without testing?

* poteltially releasable 

* Potentially!! (sorry, my smartphone`s auto correct)

I like answer it depends :)

First of all lets back to the roots about DoD.

In short DoD, is shared understanding within the Scrum Team on what it takes to make your Product increment releasable.

Do you need test your product to be releasable and meet DoD of ST/organization standards? 

Does definition of Done must include testing ? It is recommended though, but I dont think it as must as it may vary with the context of dev team and organization. Thoughts ?

Why would the need to assure the immediate usability of each increment vary by context? Can you provide an example where the quality assurance that testing provides wouldn't matter?

If your organization/team is confident in leaving out testing, then none of us can say it is wrong.  The Definition of Done is the team's agreement and communication to outside the team.  So they can decide what they want to agree to and communicate.

With that being said, I have never seen a Definition of Done for a software product that didn't include some statements related to the work completed to validate and ensure quality.  Testing is usually mentioned in some way but I have also seen "All acceptance criteria is met" when teams utilize User Stories with Acceptance Criteria defined.  While not explicit to testing, in order to determine if the criteria is met, the has to be some way of validating that and that usually involves some type of testing. 

A side benefit of a Definition of Done is that it helps the team instill a level of trust that they are doing good work.  I would have a hard time trusting the work a team does if they didn't do some level of validations.  

I think "test" is necessary to ensure quality. But if a feature does not need to be tested and the team guarantees this, the Definition of Done can be considered without testing.

If testing is not part of the workflow to get to Done, why is time and money being spent on it?

However ...
Sometimes is always. Make it part of your workflow, and if it's not done, document that fact in the same way you would do or document testing.