Testers on any project—not just agile projects—can work with programmers and test new pieces of functionality as soon as those pieces become available. Pair testing with a programmer can be a shared learning experience. Testers work closely with programmers to understand some of the risks and complexity of each feature. By reviewing unit tests and their functionality with testers, programmers learn to write more effective unit tests that support stronger code design. In turn, testers learn what has been already tested, allowing them to concentrate on higher-level business-facing tests. This approach prevents duplicated effort and increases the team's efficiency.
Another role in which testers excel is that of information provider. On traditional projects, testers have learned how to look at test results and present the information to the stakeholders in an understandable format. When testers are treated as equal partners in the software development team, the testers can expand this skill to give continual feedback to the whole team—not just the project manager.
Project managers are generally the folks who report team progress to the stakeholders outside the project team. They rely heavily on metrics in order to tell them the story. This is another area where testers provide useful information. They're expert at producing feedback that gives everyone on both the technical and business teams a full picture of project progress. For example, testers can produce charts showing how many tests are written, how many are being executed, and how many are passing.
Collaboration comes naturally to testers, as they've always worked together to make sure that the product has been tested end to end. Let the testers expand this skill to include collaboration with programmers, customers, and the rest of the team. Collaboration is a skill worth sharing, and testers are in a great position to help teams learn. Of course, the whole development team collaborates with customers, but testers often spend the most time with them, helping customers learn how to write acceptance tests and understand the possibilities.