Which option signifies a higher level of testing independence?

Outsourcing testing signifies a higher level of testing independence because it involves delegating the testing activities to an external organization that specializes in testing. This external team typically has no direct affiliation with the product development process, which helps eliminate biases that might arise from internal teams who may have vested interests in the success of the product.

When testing is outsourced, the external test specialists bring a fresh perspective, objective judgment, and specialized expertise, which enhances the reliability and credibility of the testing results. This independence is crucial in identifying defects and ensuring that requirements are met without any influence from those who are involved in the development process.

In contrast, the other options signify varying degrees of influence from internal teams. For example, while a separate test team can maintain some level of independence, they may still be affected by their proximity to the development team. Similarly, testing performed by the business often reflects a stakeholder's perspective, which can introduce bias towards the product's functionality rather than an impartial evaluation of its quality. Non-functional testing by external test specialists, while valuable, does not inherently provide the same level of overall independence as full outsourcing of the entire testing process.