No abstract

Test suite prioritization techniques modify the order in which tests within a test suite run. The goal is to order tests such that they detect faults as early as possible in the test execution cycle. Prioritization by combinatorial interaction coverage is a recent criterion that has been useful for prioritizing test suites for GUI and web applications. While studies show that this prioritization criterion can be valuable, previous studies compute the interaction coverage without considering the cost of individual tests. This paper proposes a new cost-based combinatorial interaction coverage metric, an algorithm to compute the new metric, and an empirical study with three subject web applications. Two of our studies show that prioritization by the new metric improves the rate at which faults are detected in relation to cost. A third study reveals an interesting result that the success of the cost-based metric is influenced by the distribution of t-tuples in the selected test cases.

Message passing programs commonly use buffers to avoid unnecessary synchronizations and to improve performance by overlapping communication with computation. Unfortunately, using buffers makes the program no longer portable, potentially unable to complete on systems without a sufficient number of buffers. Effective buffer use entails that the minimum number needed for a safe execution be allocated.We explore a variety of problems related to buffer allocation for safe and efficient execution of message passing programs. We show that determining the minimum number of buffers or verifying a buffer assignment are intractable problems. However, we give a polynomial time algorithm to determine the minimum number of buffers needed to allow for asynchronous execution. We extend these results to several different buffering schemes, which in some cases make the problems tractable.

With the commercial development of multicore processors, the challenges of writing multithreaded programs to take advantage of these new hardware architectures are becoming more and more pertinent. Concurrent programming is necessary to achieve the performance that the hardware offers. Traditional approaches present concurrency as an advanced topic: they have proven difficult to use, reason about with confidence, and scale up to high levels of concurrency. This article reviews process-oriented design, based on Hoare's algebra of Communicating Sequential Processes (CSP), and proposes that this approach to concurrency leads to solutions that are manageable by novice programmers; that is, they are easy to design and maintain, that they are scalable for complexity, obviously correct, and relatively easy to verify using formal reasoning and/or model checkers. These solutions can be developed in conventional programming languages (through CSP libraries) or specialized ones (such as occam-π) in a manner that directly reflects their formal expression. Systems can be developed without needing specialist knowledge of the CSP formalism, since the supporting mathematics is burnt into the tools and languages supporting it. We illustrate these concepts with the Santa Claus problem, which has been used as a challenge for concurrency mechanisms since 1994. We consider this problem as an example control system, producing external signals reporting changes of internal state (that model the external world). We claim our occam-π solution is correct-by-design, but follow this up with formal verification (using the FDR model checker for CSP) that the system is free from deadlock and livelock, that the produced control signals obey crucial ordering constraints, and that the system has key liveness properties.

No abstract