Finite-state verification techniques, such as model checking, have shown promise as a cost-effective means for finding defects in hardware designs. To date, the application of these techniques to software has been hindered by several obstacles. Chief among these is the problem of constructing a finite-state model that approximates the executable behavior of the software system of interest. Current best-practice involves handconstruction of models which is expensive (prohibitive for all but the smallest systems), prone to errors (which can result in misleading verification results), and difficult to optimize (which is necessary to combat the exponential complexity of verification algorithms). In this paper, we describe an integrated collection of program analysis and transformation components, called Bandera, that enables the automatic extraction of safe, compact finite-state models from program source code. Bandera takes as input Java source code and generates a program model in the input language of one of several existing verification tools; Bandera also maps verifier outputs back to the original source code. We discuss the major components of Bandera and give an overview of how it can be used to model check correctness properties of Java programs.

The majority of work carried out in the formal methods community throughout the last three decades has (for good reasons) been devoted to special languages designed to make it easier to experiment with mechanized formal methods such as theorem provers, proof checkers and model checkers. In this paper we will attempt to give convincing arguments for why we believe it is time for the formal methods community to shift some of its attention towards the analysis of programs written in modern programming languages. In keeping with this philosophy we have developed a verification and testing environment for Java, called Java PathFinder (JPF), which integrates model checking, program analysis and testing. Part of this work has consisted of building a new Java Virtual Machine that interprets Java bytecode. JPF uses state compression to handle big states, and partial order and symmetry reduction, slicing, abstraction, and runtime analysis techniques to reduce the state space. JPF has been applied to a real-time avionics operating system developed at Honeywell, illustrating an intricate error, and to a model of a spacecraft controller, illustrating the combination of abstraction, runtime analysis, and slicing with model checking.

This paper presents Korat, a novel framework for automated testing of Java programs. Given a formal specification for a method, Korat uses the method precondition to automatically generate all nonisomorphic test cases bounded by a given size. Korat then executes the method on each of these test cases, and uses the method postcondition as a test oracle to check the correctness of each output. To generate test cases for a method, Korat constructs a Java predicate (i.e., a method that returns a boolean) from the method’s precondition. The heart of Korat is a technique for automatic test case generation: given a predicate and a bound on the size of its inputs, Korat generates all nonisomorphic inputs for which the predicate returns true. Korat exhaustively explores the input space of the predicate but does so efficiently by monitoring the predicate’s executions and pruning large portions of the search space. This paper illustrates the use of Korat for testing several data structures, including some from the Java Collections Framework. The experimental results show that it is feasible to generate test cases from Java predicates, even when the search space for inputs is very large. This paper also compares Korat with a testing framework based on declarative specifications. Contrary to our initial expectation, the experiments show that Korat generates test cases much faster than the declarative framework.

We show how model checking and symbolic execution can be used to generate test inputs to achieve structural coverage of code that manipulates complex data structures. We focus on obtaining branch-coverage during unit testing of some of the core methods of the red-black tree implementation in the Java TreeMap library, using the Java PathFinder model checker. Three di#erent test generation techniques will be introduced and compared, namely, straight model checking of the code, model checking used in a black-box fashion to generate all inputs up to a fixed size, and lastly, model checking used during white-box test input generation. The main contribution of this work is to show how e#cient white-box test input generation can be done for code manipulating complex data, taking into account complex method preconditions.

Systematic state-space exploration is a powerful technique for veri cation of concurrent software systems. Most work in this area deals with manually-constructed models of those systems. We propose a framework for applying state-space exploration to multi-threaded distributed systems written in standard programming languages. It generalizes Godefroid's work on VeriSoft, which does not handle multi-threaded systems, and Bruening's work on ExitBlockRW, which does not handle distributed (multi-process) systems. Unlike ExitBlockRW, our search algorithms incorporate powerful partial-order methods, guarantee detection of deadlocks, and guarantee detection of violations of the locking discipline used to avoid race conditions in accesses to shared variables. 1

We present TestEra, a novel framework for automated testing of Java programs. TestEra automatically generates all non-isomorphic test cases, within a given input size, and evaluates correctness criteria. As an enabling technology, TestEra uses Alloy, a first-order relational language, and the Alloy Analyzer. Checking a program with TestEra involves modeling the correctness criteria for the program in Alloy and specifying abstraction and concretization translations between instances of Alloy models and Java data structures. TestEra produces concrete Java inputs as counterexamples to violated correctness criteria. This paper discusses TestEra's analyses of several case studies: methods that manipulate singly linked lists and red-black trees, a naming architecture, and a part of the Alloy Analyzer.

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. Despite recent advances in model checking and in adapting model checking techniques to software, the state explosion problem remains a major hurdle in applying model checking to software. Recent work in automated program abstraction has shown promise as a means of scaling model checking to larger systems. Most common abstraction techniques compute an upper approximation of the original program. Thus, when a specification is found true for the abstracted program, it is known to be true for the original program. Finding a specification to be false, however, is inconclusive since the specification may be violated on a behavior in the abstracted program which is not present in the original program. We have extended an explicit-state model checker, Java PathFinder (JPF), to analyze counter-examples in the presence of abstractions. We enhanced JPF to search for "feasible" counter-examples during model checking. Alternatively, an abstract counter-example can be used to guide the simulation of the concrete computation and thereby check feasibility of the counter-example. We demonstrate the effectiveness of these techniques on counter-examples from checks of several multi-threaded Java programs. 1

Research on how to reason about correctness properties of software systems using model checking is advancing rapidly. Work on extracting finite-state models from program source code and on abstracting those models is focused on enabling the tractable checking of program properties such as freedom from deadlock and assertion violations. For the most part, the problem of specifying more general program properties has not been considered. In this paper

Research on how to reason about correctness properties of software systems using model checking is advancing rapidly. Work on extracting finite-state models from program source code and on abstracting those models is focused on enabling the tractable checking of program properties such as freedom from deadlock and assertion violations. For the most part, the problem of specifying more general program properties has not been considered.