How much testing is relevant in an agile scenario?

Testing is as relevant in an agile scenario if not more than a traditional software development scenario. Testing is the headlight of the agile project showing where the project is standing now and the direction it is headed. Testing provides the required and relevant information to the teams to take informed and precise decisions. The testers in agile frameworks get involved in much more than finding software bugs, anything that can bug the potential user is a issue for them but testers do not make the final call, it is the entire team that discusses over it and takes a decision over a potential issues.
A firm belief of agile practitioners is that any testing approach does not assure quality, it's the team that does or does not do it, so there is a heavy emphasis on the skill and attitude of the people involved.
Agile testing is not a game of gotcha, it's about finding ways to set goals rather than focus on mistakes.
Among the agile methodologies, XP i.e. Extreme Programming components are:
- Test First Programming
- Pair Programming
- Short iterations and release.
- Re-factoring
- User Stories
- Acceptance Testing

Test-First Programming

- Developers write unit tests before coding. It has been noted that this kind of approach motivates the coding, speeds coding and also improves design results in better designs.
- It supports a practice called re-factoring.
- Agile practitioners prefer tests to text for describing system behavior. Tests are more precise than human language and they are also a lot more likely to be updated when the design changes. How many times have you seen design documents that no longer accurately described the current workings of the software? Out-of-date design documents look pretty much like up-to-date documents. Out-of-date tests fall.
- Many open source tools like xUnit have been developed to support this methodology.