Cross-functional teamwork is an important organizational and behavioral best practice for a tester in the SCRUM team that should have also been practiced when using the sequential model. Cross-functional teamwork means that all team members, regardless of their functional roles, collaborate and share their skills and knowledge to achieve a common goal. In the context of testing, this means that testing is not seen as a separate activity or phase, but as an integral part of the development process. All team members contribute to testing in various ways, such as:

Involving people with the test strategy, test planning and execution as well as test reporting. This can help ensure that the testing activities are aligned with the business objectives, the user needs, and the technical requirements. It can also help improve the test coverage, the test quality, and the test efficiency.

Sharing the responsibility for testing among the team members. This can help reduce the workload and the dependency on a single tester or a testing team. It can also help increase the feedback and the communication among the team members, and foster a culture of quality and learning.

Leveraging the diverse skills and perspectives of the team members. This can help enhance the test design and the test execution by applying different techniques, tools, and approaches. It can also help identify and address the risks, the issues, and the opportunities for improvement from various angles. References: ISTQB® Foundation Level Agile Tester Syllabus1, Section 1.2.1, page 9; ISTQB® Glossary of Testing Terms2, version 4.0, page 16.