VSCode LCOV

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

Live coverage 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

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	∅	∅
example(1)	✓	∅
example(0)	∅	✓
example(0), example(1)	✓	✓

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	∅	∅	∅	∅
example(0,0)	∅	✓	✓	∅
example(0,1)	∅	✓	✓	∅
example(1,0)	∅	✓	✓	✓
example(1,1)	✓	∅	✓	✓
example(0,0), example(0,1)	∅	✓	✓	∅
example(0,0), example(1,0)	∅	✓	✓	✓
example(0,0), example(1,1)	✓	✓	✓	✓
example(0,1), example(1,0)	∅	✓	✓	✓
example(0,1), example(1,1)	✓	✓	✓	✓
example(1,0), example(1,1)	✓	✓	✓	✓
example(0,0), example(0,1), example(1,0)	∅	✓	✓	✓
example(0,0), example(0,1), example(1,1)	✓	✓	✓	✓
example(0,0), example(1,0), example(1,1)	✓	✓	✓	✓
example(0,1), example(1,0), example(1,1)	✓	✓	✓	✓

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	∅	∅	∅	∅	∅
example(0,0,0)	∅	✓	✓	∅	∅
example(1,0,0)	∅	✓	✓	✓	∅
example(1,1,0)	∅	✓	✓	✓	✓
example(1,1,1)	✓	∅	✓	✓	✓