Tuesday, October 25, 2011

ScriptCover makes Javascript coverage analysis easy

By Ekaterina Kamenskaya, Software Engineer in Test, YouTube

Today we introduce the Javascript coverage analysis tool, ScriptCover. It is a Chrome extension that provides line-by-line Javascript code coverage statistics for web pages in real time without any user modifications required. The results are collected both when the page loads and as users interact with it. The tool reports details about total web page coverage and for each external/internal script, as well as annotated code sources with individually highlighted executed lines.

Short report in Chrome extension’s popup, detailing both overall scores and per-script coverage.

Main features:
  • Report current and previous total Javascript coverage percentages and total number of instrumented code instructions.
  • Report Javascript coverage per individual instruction for each internal and external script.
  • Display detailed reports with annotated Javascript source code.
  • Recalculate coverage statistics while loading the page and on user actions.
Sample of annotated source code from detailed report. First two columns are line number and number of times each instruction has been executed.

Here are the benefits of ScriptCover over other existing tools:
  • Per instructions coverage for external and internal scripts: The tool formats original external and internal Javascript code from ‘<script>’ tags to ideally place one instruction per line and then calculates and displays Javascript coverage statistics. It is useful even when the code is compressed to one line.

  • Dynamic: Users can get updated Javascript coverage statistics while the web page is loading and while interacting with the page.

  • Easy to use: Users with different levels of expertise can install and use the tool to analyse coverage. Additionally, there is no need to write tests, modify the web application’s code, save the inspected web page locally, manually change proxy settings, etc. When the extension is activated in a Chrome browser, users just navigate through web pages and get coverage statistics on the fly.

  • It’s free and open source!
Want to try it out? Install ScriptCover and let us know what you think.

We envision many potential features and improvements for ScriptCover. If you are passionate about code coverage, read our documentation and participate in discussion group. Your contributions to the project’s design, code base and feature requests are welcome!


  1. I can't check out the source code. Every time I run "git clone https://code.google.com/p/script-cover/", I get following output:

    Initialized empty Git repository in /home/jboss/tmp/script-cover/.git/
    fatal: https://code.google.com/p/script-cover//info/refs not found: did you run git update-server-info on the server?

    I would really like to give this extension a try!

  2. Application Security, Membership

    Some of time i try to use this but not got success, but will say it's good information for the java developers for better understanding. Thanks for sharing.


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