Automatically Assessing and Extending Code Coverage for NPM Packages

Abstract

Typical Node.js applications extensively rely on packages hosted in the npm registry. As such packages may be used by thousands of other packages or applications, it is important to assess their code coverage. Moreover, increasing code coverage may help detect previously unknown issues. In this paper, we introduce TESA, a new tool that automatically assembles a test suite for any package in the npm registry. The test suite includes 1) tests written for the target package and usually hosted in its development repository, and 2) tests selected from dependent packages. The former tests allow assessing the code coverage of the target package, while the latter ones can increase code coverage by exploiting third-party tests that also exercise code in the target package. We use TESA to assess the code coverage of 500 popular npm packages. Then, we demonstrate that TESA can significantly increase code coverage by including tests from dependent packages. Finally, we show that the test suites assembled by TESA increase the effectiveness of existing dynamic program analyses to identify performance issues that are not detectable when only executing the developer's tests.

Hypermedia-based software architecture enables Test-Driven Development

“…Google, for example, reported a practice in which 60% coverage is “acceptable,” 75% is “commendable,” and 90% is “exemplary.” 19 , 20 Other sources refer to an informal 80% standard. 64 , 80 CORE Browser’s backend code coverage approaches 80% and is commendable by Google’s standard. 20 All backend components meet or exceed Google’s acceptable standard except heaserver-accounts due to limitations in Moto that prevent complete testing of its features.…”