Risk-based testing (RBT) is a type of software testing that functions as an organizational principle used to prioritize the tests of features and functions in software, based on the risk of failure, the function of their importance and likelihood or impact of failure. In theory, there are an infinite number of possible tests. Risk-based testing uses risk (re-)assessments to steer all phases of the test process, i.e., test planning, test design, test implementation, test execution and test evaluation. This includes for instance, ranking of tests, and subtests, for functionality; test techniques such as boundary-value analysis, all-pairs testing and state transition tables aim to find the areas most likely to be defective.