Code coverage with Mocha

Question

I am using Mocha for testing my NodeJS application  I am not able to figure out how to use its code coverage feature  I tried googling it but did not find any proper tutorial  Please help

User · Answer

Blanket js works perfect too   npm install --save-dev blanket  in front of your test tests js  require  blanket         pattern  function  filename            return   node modules  test filename               run mocha -R html-cov  gt  coverage html

User · Answer

You need an additional library for code coverage  and you are going to be blown away by how powerful and easy istanbul is  Try the following  after you get your mocha tests to pass  npm install nyc  Now  simply place the command nyc in front of your existing test command  for example       quot scripts quot          quot test quot    quot nyc mocha quot

User · Answer

Now  2021  the preferred way to use istanbul is via its  quot state of the art command line interface quot  nyc  Setup First  install it in your project with npm i nyc --save-dev  Then  if you have a npm based project  just change the test script inside the scripts object of your package json file to execute code coverage of your mocha tests       quot scripts quot          quot test quot    quot nyc --reporter text mocha quot         Run Now run your tests npm test  and you will see a table like this in your console  just after your tests output   Customization Html report Just use nyc --reporter html  instead of text  Now it will produce a report inside   coverage index html  Report formats Istanbul supports a wide range of report formats  Just look at its reports library to find the most useful for you  Just add a --reporter REPORTER NAME option for each format you want  For example  with nyc --reporter html --reporter text  you will have both the console and the html report  Don t run coverage with npm test Just add another script in your package json and leave the test script with only your test runner  e g  mocha        quot scripts quot          quot test quot    quot mocha quot        quot test-with-coverage quot    quot nyc --reporter text mocha quot         Now run this custom script npm run test-with-coverage  to run tests with code coverage  Force test failing if code coverage is low Fail if the total code coverage is below 90   nyc --check-coverage --lines 90   Fail if the code coverage of at least one file is below 90   nyc --check-coverage --lines 90 --per-file

[node.js] Code coverage with Mocha

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