No coverage nyc mocha

Question

I am just unable to figure out why test coverage is 0 even though test case is passing. I have a script in package.json:

"nyctest": "node --max_old_space_size=4096 node_modules/nyc/bin/nyc.js --reporter=text mocha"

When I run npm run nyctest

My test pass, but coverage is 0 percent.

Following is the test and the file is it testing:

test.js

var chai = require('chai');
var sinon = require('sinon');
var sinonChai = require('sinon-chai');
chai.should();
chai.use(sinonChai);
var application = require('../../../src/main/resources/static/js/components/app.js');

describe('sample return testing', function(){
    it('should return true', function(){
        application.sample.returnValue().should.equal(true);
    })
});

app.js

const sample = {
    returnValue: function () {
        return true;
    }
};

module.exports = {sample};

Appreciate any help.

[Use the `--all` flag to include files that have not been required in your tests](https://github.com/istanbuljs/nyc#use-the---all-flag-to-include-files-that-have-not-been-required-in-your-tests) — laggingreflex, May 22 '18 at 10:33

score 11 · Answer 1 · answered Nov 04 '21 at 23:02

11

I hit this issue when using "type": "module" (ES Modules) with TypeScript.

There is an issue with the nyc (Instanbul) loader for ESM modules. The recommended solution is to abandon nyc and use the native coverage now built into Node 13 and above: c8.

https://github.com/bcoe/c8

answered Nov 04 '21 at 23:02

mckoss

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I have no way to test this as nodejs days are long gone for me. I can only upvote your answer. Thanks for the help! – Faraz Nov 05 '21 at 07:50
This is the best answer if you managing a Typescript project. Could've saved hours if I found this answer earlier. – Samitha Nanayakkara Mar 04 '23 at 19:30

score 8 · Answer 2 · edited May 13 '21 at 12:08

8

By August 2020: two things:

You need to add the --all parameter.
Preferably use the .nycrc file in order to not have a long command line in your package.json as follows:

The minimal .nycrc file:

{
  "all": true,
  "include": [
    "test/**.js"
  ],
  "exclude": []
}

edited May 13 '21 at 12:08

Lee Goddard

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answered Aug 20 '20 at 10:02

Stéphane de Luca

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where is this file located? – Umakanth Pendyala Oct 14 '22 at 06:54

score 4 · Answer 3 · edited Dec 25 '20 at 04:15

4

You need to modify your nyctest command with --all flag, as follows:

"nyctest": "nyc --reporter=lcov --reporter=text-lcov --all -x \"./node_modules/*\" -x \"./coverage/*\" check-coverage --lines 10 --functions 90 npm run unittest"

So with --all flag, all files are fetched

edited Dec 25 '20 at 04:15

lbragile

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answered Jun 21 '18 at 12:28

Clinton Roy

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score 3 · Answer 4 · answered Jun 06 '20 at 23:16

3

In my case, the problem was that .nyrc configuration contained "instrument": false. Removing this brought back coverage reports.

answered Jun 06 '20 at 23:16

Adam Reis

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score 3 · Answer 5 · answered Apr 09 '21 at 02:10

TL;DR: Try useSpawnWrap: true in your nyc config.

The root cause of the issue is due to the way nyc instruments the files for coverage. It does this by watching it's child process and keeping track of what code is ran. This is why you pass mocha to nyc

You can test if this is the case by adding the --show-process-tree flag to nyc, as described in the nyc docs. If you see "nyc" at the bottom of the output, but nothing under it, you will know this is your issue.

Now, the note above explains how to work around this (useSpawnWrap: true), but what causes it? This GitHub issue comment partly explains what is happening, and this comment explains how pnpm broke this ability. In my case I am hitting this with nvm, though I sure it is the same root cause, something is affecting either path, or the process.env.NODE_OPTIONS environmental variable.

I hope this more detailed explanation helps you troubleshoot issues like this in the future.

score 1 · Answer 6 · answered Jul 24 '19 at 06:03

My case is a little different,

I have installed mocha globally and when nyc referring mocha globally it does't show anything in the coverage report.

I got result when running

nyc node_modules/.bin/mocha

It is a known issue and refer here https://github.com/istanbuljs/nyc/issues/1029#issuecomment-514174340

No coverage nyc mocha

6 Answers6

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