It is a standard practice in Software development companies to have separate environments for developers and testers because
- If QA is using a developer’s environment, which is likely changing. It is hard to control the state of the environment with different individuals working against it.
- Commonly, QA environments mimic more closely production environments than do development environments. If QA tests in an developers environment its more likely testing the functionality where it is created . But, if QA tests in a separate testing environment it typically helps to see different defects than developers and ensure functionality is valid in multiple environments.
- Developers generally have lots of tools and things running in their environment that could influence QA validation.