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This is a playground to test code. It runs a full Node.js environment and already has all of npm’s 400,000 packages pre-installed, including coverify with all npm packages installed. Try it out:

var coverify = require("coverify")

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coverify v1.4.1

code coverage browserify transform


code coverage browserify transform

testling badge

build status


Suppose we have a test.js:

var test = require('tape');
var foo = require('./foo.js');

test('beep boop', function (t) {
    foo(function (err, x) {
        if (err) deadCode();
        t.equal(x * 5, 555);

and a foo.js:

module.exports = function (cb) {
    var i = 0;
    var iv = setInterval(function () {
        if (i++ === 10 || (false && neverFires())) {
            cb(null, 111);
    }, 10);

Now with browserify just do:

$ browserify -t coverify example/test.js --bare | node | coverify
TAP version 13
# beep boop
ok 1 should be equal

# tests 1
# pass  1

# ok

# /home/substack/projects/coverify/example/test.js: line 7, column 16-28

  if (err) deadCode();

# /home/substack/projects/coverify/example/foo.js: line 3, column 35-48

  if (i++ === 10 || (false && neverFires())) {

# coverage: 34/36 (94.4400%)

browserify compiled our test.js file, then testling ran our code in a local headless browser (we also could have used node), and then coverify parsed the test output for code coverage data and printed some nicely formatted results on stderr. Hooray!

and the exit code is non-zero because the coverage wasn't 100%:

$ echo $?

If you want to run code coverage for browser tests, you can use the testling command:

$ browserify -t coverify example/test.js | testling | coverify

and the output and exit codes work exactly the same, except the code is running in a browser instead of node.


var coverify = require('coverify')
var parse = require('coverify/parse')

Usually you can just do browserify -t coverify to get code coverage but you can also use the api directly if you want to use this code directly.

var stream = coverify(file, opts={})

Return a transform stream for file that will instrument the input source file using console.log().

To use a different function from console.log(), pass in opts.output.

var stream = parse(cb)

Return a transform stream that accepts test output as input and looks for lines starting with COVERAGE and COVERED to generate a coverage report in cb(err, coverage, counts).

coverage is an object that maps filenames from the bundle files to arrays of coverage data.

counts is an object mapping filenames to objects with expr and total fields for how many expressions were covered and how many expressions were present.

All of the non-/^(COVERAGE|COVERED)\s/ lines are passed through from the input to the output.

Here is some example coverage data that you can generate with coverify --json:

  "/home/substack/projects/coverify/example/test.js": [
      "range": [
      "lineNum": 7,
      "column": [
      "line": "        if (err) deadCode();",
      "code": "deadCode();"
  "/home/substack/projects/coverify/example/foo.js": [
      "range": [
      "lineNum": 3,
      "column": [
      "line": "        if (i++ === 10 || (false && neverFires())) {",
      "code": "neverFires()"


usage: coverify OPTIONS



    Suppress normal output and print json coverage data to stdout.

  -q, --quiet

    Don't print non-coverage input back out to stdout and print coverage
    output to stdout instead of stderr.

  -c, --color

    Use color in the output. Default: true if stdout is a TTY.


    Always print non-coverage input back out to stdout.

  -o FILE, --output FILE

    Print coverage data to FILE. Use "@2" for stderr (the default) and
    "@1" or "-" for stdout.


With npm do:

npm install coverify

to get the browserify transform module.

When you compile your tests with browserify you can just do:

browserify -t coverify ...

You will also need the coverify command for parsing the test output:

npm install -g coverify



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