Foundation Level CTFL-Foundation Book

White box testing techniques, also known as structure-based techniques, focus on the internal structure of the software. Decision testing (C) is a white box technique that involves creating test cases to execute specific decision points in the code, such as conditional statements. This ensures that all possible paths through the code are tested, helping to identify defects related to the control flow of the application. Other techniques listed, such as use case testing and state transition testing, are black box techniques that focus on the software's functionality from the user's perspective​​.

The failure rate in testing already completed is a useful metric to monitor progress along with test preparation and execution. It provides insight into the effectiveness of the tests and the quality of the product, helping to identify areas that may require additional attention or resources.

It is generally not feasible to perform exhaustive testing due to time and resource constraints. Instead, testing efforts should be focused using risk analysis and priorities to ensure the most critical areas are tested thoroughly. This approach helps in maximizing the effectiveness of the testing process while managing resources efficiently.

Decision table testing is a black-box test design technique used to test system requirements and to ensure that different combinations of inputs result in appropriate outputs. It is especially useful for testing complex business logic and rules where various combinations of conditions need to be verified.