Unit Testing Asynchronous Code: Three Solutions for Better Tests

摘要

Asynchronous programming has become more and more important during the last decade. Whether for CPU-based parallelism or IO-based concurrency, developers are employing asynchrony to help make the most of the resources available and, ultimately, do more with less. More responsive client applications and more scalable server applications are all within reach. Software developers have learned a lot of design patterns for effectively building synchronous functionality, but best practices for designing asynchronous software are relatively new, though the support provided by programming languages and libraries for parallel and concurrent programming has dramatically improved with the release of the Microsoft .NET Framework 4 and 4.5. While there's already quite a lot of good advice for using the new techniques (see "Best Practices in Asynchronous Programming" at bit.ly/1ulDCil and "Talk: Async Best Practices" at bit.ly/1DsFuMi), best practices for designing the internal and external APIs for applications and libraries with language features like async and await and the Task Parallel Library (TPL) are still unknown to many developers.