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VSCode LCOV

Renders Line and Branch coverage from lcov.info files interactively.

Live coverage info

Live info

Features

  • loosely coupled, just point it to a lcov.info file and you're in business!
  • can read multiple lcov.info files (e.g. one for the entire project, one for the last single test run)
  • generates a Coverage Report
  • supports watching certain files and executing a command (e.g. run test on file change)
  • supports JavaScript source maps

Coverage Report

  • Ctrl+T or Cmd+T then choose Show Coverage Report Coverage Report

Setting up

  • There is a complete simple example at https://github.com/alexandrudima/vscode-lcov/tree/master/examples/fizzbuzz
  • There are many tools that can generate lcov.info files
  • I have tested lcov.info files generated by istanbul e.g.istanbul cover --report lcovonly ./node_modules/mocha/bin/_mocha -- -R spec test.js
  • Configure the paths to your lcov.info files via the setting lcov.path. e.g:
"lcov.path": [
    "./.build/coverage/lcov.info",
    "./.build/coverage-single/lcov.info"
]
  • Live coverage via the setting lcov.watch. e.g. to execute a certain command any time a .js file is changed:
"lcov.watch": [{
    "pattern": "**/*.js",
    "command": "npm run test-coverage"
}]
  • Live coverage can be switched on via Ctrl+T or Cmd+T then choose Enable watchers
  • JavaScript sourcemaps via the setting lcov.sourceMaps.
"lcov.sourceMaps": true

Troubleshooting

  • View > Output and choose lcov.

Branch coverage: Configuration

"lcov.branchCoverage": "off" or "simple" (default) or "full"

Branch coverage: A single boolean expression

exports.example = function (a) {
	if (a) {
		console.log('1');
	}
}

The above source code contains a single branch block consisting of two branches.

Test Code if taken else taken "simple" "full"
//no calls image image
example(1) image image
example(0) image image
example(0), example(1) image image

Branch coverage: A binary boolean expression

exports.example = function (a, b) {
	if (a && b) {
		console.log('1');
	}
}

For the table columns:

  • IF = if taken
  • ELSE = else taken
  • A? = a evaluated
  • B? = b evaluated
Test Code IF ELSE A? B? "simple" "full"
//no calls image image
example(0,0) image image
example(0,1) image image
example(1,0) image image
example(1,1) image image
example(0,0), example(0,1) image image
example(0,0), example(1,0) image image
example(0,0), example(1,1) image image
example(0,1), example(1,0) image image
example(0,1), example(1,1) image image
example(1,0), example(1,1) image image
example(0,0), example(0,1), example(1,0) image image
example(0,0), example(0,1), example(1,1) image image
example(0,0), example(1,0), example(1,1) image image
example(0,1), example(1,0), example(1,1) image image

Branch coverage: A ternary boolean expression

exports.example = function (a, b, c) {
	if (a && b && c) {
		console.log('1');
	}
}

For the table columns:

  • IF = if taken
  • ELSE = else taken
  • A? = a evaluated
  • B? = b evaluated
  • C? = c evaluated
Test Code IF ELSE A? B? C? "full"
//no calls image
example(0,0,0) image
example(1,0,0) image
example(1,1,0) image
example(1,1,1) image