The act of reviewing a test plan is a Quality Assurance function. Therefore my answer is b) QA. This is not an easy call because a test plan includes elements of Quality Assurance and Quality Control. Please read on for details.
Quality Assurance (QA) attempts to improve and stabilize processes in order to minimize the issues that produce defects. QA processes also strive to assure that a product service or system meets its intended purposes focusing on external requirements and expectations. This can be expressed by "Are you building the right thing?" Quality Assurance 1) deals with process 2) is proactive 3) is a staff function and 4) helps to prevent defects.
Quality Control (QC) emphasizes the testing of products to uncover defects as well as reporting their findings to management who make the decision to allow or deny product release. QC evaluates whether or not a product service or system complies with regulations specifications or conditions imposed at the start of a development phase focusing on internal requirements and expectations. This can be expressed by "Are you building the thing right?" Quality Control 1) deals with product 2) is reactive 3) is a line function and 4) is meant to find defects.
Consider these definitions in terms of a typical software QA and Test group.
1) Whenever members of QA and Test do anything to improve internal processes in order to minimize defects they are performing Quality Assurance activities.
2) Whenever members of QA and Test align test cases with functional requirements they are performing Quality Assurance activities.
3) Whenever members of QA and Test uncover defects and report their findings so that management can make informed decisions about the corresponding software release they are performing Quality Control activities.
A test plan describes the test strategies that will be employed throughout a software development project. The act of developing a test plan is a Quality Assurance activity. Nevertheless the intended purpose of the test plan is to ultimately help testers perform their Quality Control activities.
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