Lev Nachmanson

Model-based testing of object-oriented reactive systems with spec explorer

Testing is one of the costliest aspects of commercial software development. Model-based testing is a promising approach addressing these deficits. At Microsoft, model-based testing technology developed by the Foundations of Software Engineering group in Microsoft Research has been used since 2003. The second generation of this tool set, Spec Explorer, deployed in 2004, is now used on a daily basis by Microsoft product groups for testing operating system components, .NET framework components and other areas. This chapter provides a comprehensive survey of the concepts of the tool and their foundations.

Optimal strategies for testing nondeterministic systems

This paper deals with testing of nondeterministic software systems. We assume that a model of the nondeterministic system is given by a directed graph with two kind of vertices: states and choice points. Choice points represent the nondeterministic behaviour of the implementation under test (IUT). Edges represent transitions. They have costs and probabilities. Test case generation in this setting amounts to generation of a game strategy. The two players are the testing tool (TT) and the IUT. The game explores the graph. The TT leads the IUT by selecting an edge at the state vertices. At the choice points the control goes to the IUT. A game strategy decides which edge should be taken by the TT in each state. This paper presents three novel algorithms 1) to determine an optimal strategy for the bounded reachability game, where optimality means maximizing the probability to reach any of the given final states from a given start state while at the same time minimizing the costs of traversal; 2) to determine a winning strategy for the bounded reachability game, which guarantees that given final vertices are reached, regardless how the IUT reacts; 3) to determine a fast converging edge covering strategy, which guarantees that the probability to cover all edges quickly converges to 1 if TT follows the strategy.

Towards a Tool Environment for Model-Based Testing with AsmL

We present work on a tool environment for model-based testing with the Abstract State Machine Language (AsmL). Our environment supports semiautomatic parameter generation, call sequence generation and conformance testing. We outline the usage of the environment by an example, discuss its underlying technologies, and report on some applications conducted in the Microsoft environment.

Play to test

Testing tasks can be viewed (and organized!) as games against nature. We study reachability games in the context of testing. Such games are ubiquitous. A single industrial test suite may involve many instances of a reachability game. Hence the importance of optimal or near optimal strategies for reachability games. One can use linear programming or the value iteration method of Markov decision process theory to find optimal strategies. Both methods have been implemented in an industrial model-based testing tool, Spec Explorer, developed at Microsoft Research.

Testing concurrent object-oriented systems with spec explorer

We describe a practical model-based testing tool developed at Microsoft Research called Spec Explorer. Spec Explorer enables modeling and automatic testing of concurrent object-oriented systems. These systems take inputs as well as provide outputs in form of spontaneous reactions, where inputs and outputs can be arbitrary data types, including objects. Spec Explorer is being used daily by several Microsoft product groups. The here presented techniques are used to test operating system components and Web service infrastructure.

Edge routing with ordered bundles

We propose a new approach to edge bundling. At the first stage we route the edge paths so as to minimize a weighted sum of the total length of the paths together with their ink. As this problem is NP-hard, we provide an efficient heuristic that finds an approximate solution. The second stage then separates edges belonging to the same bundle. To achieve this, we provide a new and efficient algorithm that solves a variant of the metro-line crossing minimization problem. The method creates aesthetically pleasing edge routes that give an overview of the global graph structure, while still drawing each edge separately, without intersecting graph nodes, and with few crossings.

Improving layered graph layouts with edge bundling

We show how to improve the Sugiyama scheme by edge bundling. Our method modifies the layout produced by the Sugiyama scheme by bundling some of the edges together. The bundles are created by a new algorithm based on minimizing the total ink needed to draw the graph edges. We give several implementations that vary in quality of the resulting layout and execution time. To diminish the number of edge crossings inside of the bundles we apply a metro-line crossing minimization technique. The method preserves the Sugiyama style of the layout and creates a more readable view of the graph.

Drawing graphs with GLEE

This paper describes novel methods we developed to lay out graphs using Sugiyamas scheme [16] in a tool named GLEE. The main contributions are: a heuristic for creating a graph layout with a given aspect ratio, an efficient method of edge-crossings counting while performing adjacent vertex swaps, and a simple and fast spline routing algorithm.

Fast edge-routing for large graphs

To produce high quality drawings of graphs with nodes drawn as shapes it is important to find routes for the edges which do not intersect node boundaries. Recent work in this area involves finding shortest paths in a tangent-visibility graph. However, construction of the full tangent-visibility graph is expensive, at least quadratic time in the number of nodes. In this paper we explore two ideas for achieving faster edge routing using approximate shortest-path techniques.

Graph drawing contest report

This report describes the 19th Annual Graph Drawing Contest, held in conjunction with the 2012 Graph Drawing Symposium in Redmond, USA. The purpose of the contest is to monitor and challenge the current state of graph-drawing technology. For the first time, we introduced a graph drawing game contest and asked conference attendees to judge the games.