We present a small, formal language for specifying the behavior of simple console I/O programs. The design is driven by the concrete application case of testing interactive Haskell programs written by students. Specifications are structurally similar to lexical analysis regular expressions, but are augmented with features like global variables that track state and history of program runs, enabling expression of an interesting range of dynamic behavior. We give a semantics for our specification language based on acceptance of execution traces. From this semantics we derive a definition of the set of all traces valid for a given specification. Sampling that set enables us to mechanically check program behavior against specifications in a probabilistic fashion. Beyond testing, other possible uses of the specification language in an education context include related activities like providing more helpful feedback, generating sample solutions, and even generating random exercise tasks.

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We present the design of a framework to automatically generate a large range of different exercise tasks on Haskell-I/O programming. Automatic task generation is useful in many different ways. Manual task creating is a time consuming process, so automating it saves valuable time for the educator. Together with an automated assessment system automatic task generation allows students to practice with as many exercise tasks as needed. Additionally, each student can be given a slightly different version of a task, reducing issues regarding plagiarism that arise naturally in an e-learning environment. Our task generation is centered around a specification language for I/O behavior that we developed in an earlier work. The task generation framework, an EDSL in Haskell, provides powerful primitives for the creation of various artifacts, including program code, from specifications. We will not go into detail on the technical realization of these primitives. This article instead showcases how such artifacts and the framework as a whole can be used to build exercise tasks templates that can then be (randomly) instantiated.