There is a known bug when using Babel with Istanbul (NYC) that when you run coverage it displays coverage problems with

for imports.

For example, in my case, I had:

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import sequelize from Sequelize

and running coverage result with:

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else path not taken

It usually happens if you have in your babel.config.json the following:

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  "sourceMaps": true,

  "retainLines": true

and when you remove them the coverage jumps back with no coverage issues?

Solutions

I found few non helpful solutions for this case:

1. To remove the sourceMaps and retainLines (which I didn’t wanted).
2. To use

   1	/* istanbul ignore next */

   or

   1	/* istanbul ignore else */

   which didn’t worked
3. To add

   1	auxiliaryCommentBefore: ' istanbul ignore next '

   to Babel configuration which didn’t worked for me.

The solution I found to be the best is to use the babel plugin:

babel-plugin-istanbul

install it using

.

Then, add the following to your

:

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  "env": {

    "test": {

      "plugins": [

        "istanbul"

      ]

    }

  },

and last, update your package.json script to run coverage with BABEL_ENV variable set to

. I used cross-env for multi-OS support (Windows/Linux/Mac)

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"test": "mocha",

"coverage": "cross-env BABEL_ENV=test nyc npm run test -s",

And now the coverage working perfectly with sourceMaps and retainLines!!!