This question was asked to me in an interview to a well known consulting company. I'm not quite sure what was the correct answer for I did not receive a constructive feedback from my interviewer
I'm going to go with my standard answer: It depends.
The information that goes into a Testing Summary Report will largely be the same:
- testing performed (with an indication of coverage),
- test results in summary (often but not always x tests run, y tests passed,
- summary of outstanding bugs grouped by priority (0 critical, 0 serious, a medium, etc.)
- application status (this can vary a lot - I've used Red/Yellow/Green and go/no-go with explanations of why)
While the tests you're reporting on in an Agile environment will be lightly documented compared to those reported on in a Waterfall environment, they are still tests, and will still have results. You may also be including the outcomes of exploration sessions in your reporting (in both environments, since even in a Waterfall setting an exploratory tour of the new software is a good idea).
The format of the report will be governed by the test management tooling you're using - be it spreadsheets or full-featured ALM tools - and whether you need to modify that information for the report recipients.
The content of the report will be governed by what data and how much data the recipients need to make their decision on the future of the project.
Ultimately, it comes down to what the stakeholders who receive that report need to receive from you and your team.