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Testing is one of the costliest aspects of commercial software development. Model-based testing is a promising approach addressing these deficits. At Mi-crosoft, 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,(More)
We discuss how to perform symbolic execution of large programs in a manner that is both compositional (hence more scalable) and demand-driven. Compositional symbolic execution means finding feasible interprocedural program paths by composing symbolic executions of feasible intraprocedural paths. By demand-driven, we mean that as few intraprocedural paths as(More)
Tracing just-in-time compilers (TJITs) determine frequently executed traces (hot paths and loops) in running programs and focus their optimization effort by emitting optimized machine code specialized to these traces. Prior work has established this strategy to be especially beneficial for dynamic languages such as JavaScript, where the TJIT interfaces with(More)
We discuss the problem of path feasibility for programs manipulating strings using a collection of standard string library functions. We prove results on the complexity of this problem, including its undecidability in the general case and decidability of some special cases. In the context of test-case generation, we are interested in an efficient finite(More)
Constraints in form regular expressions over strings are ubiquitous. They occur often in programming languages like Perl and C#, in SQL in form of LIKE expressions, and in web applications. Providing support for regular expression constraints in program analysis and testing has several useful applications. We introduce a method and a tool called Rex, for(More)
Dynamically discovering likely program invariants from concrete test executions has emerged as a highly promising software engineering technique. Dynamic invariant inference has the advantage of succinctly summarizing both "expected" program inputs and the subset of program behaviors that is normal under those inputs. In this paper, we introduce a technique(More)
The world is experiencing a technology shift. In 2011, more touchscreen-based mobile devices like smartphones and tablets will be sold than desktops, laptops, and netbooks combined. In fact, in many cases incredibly powerful and easy-to-use smart phones are going to be the first and, in less developed countries, possibly the only computing devices which(More)
During the last 10 years, code inspection for standard programming errors has largely been automated with static code analysis. During the next 10 years, we expect to see similar progress in automating testing, and specifically test generation, thanks to advances in program analysis, efficient constraint solvers, and powerful computers. Three new tools from(More)
Software programs evolve throughout their lifetime undergoing various changes. While making these changes, software developers may introduce regression faults. It is desirable to detect these faults as quickly as possible to reduce the cost involved in fixing them. One existing solution is continuous testing, which runs an existing test suite to quickly(More)