Cypress V8 Coverage Plugin

this plugin aims at providing codecoverage using the chrome V8 coverage api

It is adapted from this poc

Abilities and limitation

This plugin does :

• gather coverage on multiple tests
• gather coverage on multiple files
• works with chrome
• converts coverage reports to html or lcov
• apply sourcemaps on a report generation

This plugins doesn't

• handle other browser than chrome ( for technical limitation reasons )
• cure all afflictions, make children behave, or long lost loves come back, this is not black magic 🧙‍♀️.

Usage

Configuration:

required

    {...
        "env":{
            "v8_coverage":{
                "include":["glob/**/to/your/files.*js","other/glob"],
                "src_root":"path/to/your/src/root",
                "collect_coverage_timeout":120000 //optional, this affects the final code collection step, that may timeout if your codebase is big enough
            }
        }
    }

On coverage collection we will replace the url root with the supplied src_root, and run the glob matching on the result string

Both thoses settings are required as they are used to recognize which files are to be kept amongst all the browser loaded files.

support/index.js

[...]
import "cypress_v8_coverage_plugin/support"
[...]

This allows the plugin to hook on test lifecyle events

plugins/indes.js

const cypress_v8_plugin = require("cypress_v8_coverage_plugin/plugin")
module.exports = (on, config) => {
    ...
    config = cypress_v8_plugin(on,config)
    ...
    return config
}

This registers the plugin in to cypress

Optional Collect

optional

At the end of each spec a collection spec occurs, gathering coverage data from the spec's tests. This can be a lengthy process, to reduce the run cost, you can add the skip_coverage_collection option :

    {...
        "env":{
            "v8_coverage":{
                ...,
                skip_coverage_collection:true
                ...
            }
        }
    }

And run independently the src/scripts/collectCoverage.js script to collect coverage and convert it to istanbul, while applying the sourcemap

Convertion

optional You can trigger a report convertion to the html or lcov through the convert_coverage task

This run the nyc command through npx on the generated files.

afterAll(()=>{
    cy.task("convertCoverage",'html',"./html/report/dir")//use an empty dir, this generates a lot of files
    cy.task("convertCoverage","lcov","./lcovpath.info")
})

Otherwise, you can trigger this convertion manualy using nyc or istanbul