Mutation testing of a test suite and a program provides a way to measure the quality of the test suite. In essence, mutation testing is a form of sensitivity testing: by running mutated versions of the program against the test suite, mutation testing measures the suite's sensitivity for detecting bugs that a programmer might introduce into the program. This paper introduces a technique to improve mutation testing that we call wild-caught mutants; it provides a method for creating potential faults that are more closely coupled with changes made by actual programmers. This technique allows the mutation tester to have more certainty that the test suite is sensitive to the kind of changes that have been observed to have been made by programmers in real-world cases.

Command-line tools are confusing and hard to use due to their cryptic error messages and lack of documentation. Novice users often resort to online help-forums for finding corrections to their buggy commands, but have a hard time in searching precisely for posts that are relevant to their problem and then applying the suggested solutions to their buggy command. We present NoFAQ, a tool that uses a set of rules to suggest possible fixes when users write buggy commands that trigger commonly occurring errors. The rules are expressed in a language called FIXIT and each rule pattern-matches against the user's buggy command and corresponding error message, and uses these inputs to produce a possible fixed command. NoFAQ automatically learns FIXIT rules from examples of buggy and repaired commands. We evaluate NoFAQ on two fronts. First, we use 92 benchmark problems drawn from an existing tool and show that NoFAQ is able to synthesize rules for 81 benchmark problems in real time using just 2 to 5 input-output examples for each rule. Second, we run our learning algorithm on the examples obtained through a crowd-sourcing interface and show that the learning algorithm scales to large sets of examples.

We analyze the I/O behavior of iBench , a new collection of productivity and multimedia application workloads. Our analysis reveals a number of differences between iBench and typical file-system workload studies, including the complex organization of modern files, the lack of pure sequential access, the influence of underlying frameworks on I/O patterns, the widespread use of file synchronization and atomic operations, and the prevalence of threads. Our results have strong ramifications for the design of next generation local and cloud-based storage systems.

We analyze the I/O behavior of iBench, a new collection of productivity and multimedia application workloads. Our analysis reveals a number of differences between iBench and typical file-system workload studies, including the complex organization of modern files, the lack of pure sequential access, the influence of underlying frameworks on I/O patterns, the widespread use of file synchronization and atomic operations, and the prevalence of threads. Our results have strong ramifications for the design of next generation local and cloud-based storage systems.