1. Acceptance testing performed by the customer in a controlled environment at the developer's site. The software is used by the customer in a setting approximating the target environment with the developer observing and recording errors and usage problems.

Testing of a software product or system conducted at the developer’s site by the end user.

2. Alpha testing is testing of an application when development is nearing completion. Minor design changes can still be made as a result of alpha testing. Alpha testing is typically performed by a group that is independent of the design team, but still within the company, e.g. in-house software test engineers, or software QA engineers.

3. Alpha testing is final testing before the software is released to the general public. First, (and this is called the first phase of alpha testing), the software is tested by in-house developers. They use either debugger software, or hardware-assisted debuggers. The goal is to catch bugs quickly. Then, (and this is called second stage of alpha testing), the software is handed over to us, the software QA staff, for additional testing in an environment that is similar to the intended use.