An invariant is a condition that remains true throughout the execution of a piece of code, adapted from the mathematical definition of a property that remains unchanged under transformations applied to an object or class of objects. In software, invariants function as an implicit contract or agreement about the code rather than something explicitly written, with two key categories: loop invariants (conditions true before and after each loop iteration, concerning code logic) and representation invariants (concerning data structure), the latter including class invariants that hold for all instances of a class throughout their lifetime. This concept belongs to the domain of software correctness and program verification within computer science, relating to testing methodology (including property-based testing) as a means of formally specifying and validating the assumptions developers rely on.
An invariant is a condition that remains true throughout the execution of a piece of code, adapted from the mathematical definition of a property that remains unchanged under transformations applied …