V8 Chrome Coverage

Experimental project to test extracting code coverage statistics from the v8 engine in Chrome.

How It Works

Tests are run using the wdio framework. Using the wdio lifecycle hooks as well as the @wdio/devtools-service, we startPreciseCoverage at the beginning of a test suite, and takePreciseCoverage when a test suite is completed. The coverage data is written to the .v8-coverage directory.

On test completion, a script (scripts/mergeAndResolveUrls.js) is run to convert the http urls in the coverage files into file paths. A single json file with the resolved paths are written to coverage/tmp/coverage.json.

Next the c8 tool is used to generate an lcov report. The coverage results can be viewed at coverage/lcov-report/index.html.

Notable Dependencies

• node v12 (but node versions < v16 should also work. This is a requirement of the @wdio/sync module.)
• chrome 104. If you're using a different version of chrome you'll have to install the chromedriver module matching your chrome version.

To Run

• npm run ci: This will run the test and generate the report. (Previous test reports and coverage data will be deleted!!!)
• google-chrome coverage/lcov-report/index.html: View the report.