How to collect test coverage including untested files?

[DanilAgafonov]

Is it possible to include untested files in coverage report?

Reason: I want to know how much code I have uncovered in my project overall. I want to see files for which I haven't created any tests and never imported them anywhere.

Example:
Let's say I have src/index.js file. And I run node --test --experimental-test-coverage --test-coverage-include="src/**/*" in the root of my project. My expectation: report should include index.js showing that zero lines covered with tests.

[nullswan]

Also interested ! I think this is related to nodejs/help#4487

[MoLow]

Coverage is collected using v8's takeCoverage method, which means it is only aware of code that has actually run.
this might be a feature that is possible to implement but it is impossible with the current implementation

[hernandemonteiro]

Yes, it is possible to include untested files in your coverage report, but it often requires additional configuration because many coverage tools only include files that were executed or imported during the test run by default.

To include all files, even those that were not imported or executed during the test run, you need to configure your testing or coverage tool explicitly. Here's how to do it using some common tools and frameworks:

---

For Node.js with --experimental-test-coverage:

The --experimental-test-coverage option in Node.js collects coverage for files executed during the test run. By default, it won't include files that weren't executed. To include all files, you need to ensure they are part of the coverage scope explicitly:

1. Use --test-coverage-include to include all files (you are already doing this):

   node --test --experimental-test-coverage --test-coverage-include="src/**/*"

2. If the files are still not included, consider importing them in a "setup" file to ensure they are loaded into the test environment. For example:

   // setup.js
   import './src/index.js';

   Then, run your tests with this setup file to ensure untested files are at least loaded:

   node --test setup.js --experimental-test-coverage

---

With nyc (Istanbul):

If you're using nyc (a popular coverage tool), you can explicitly configure it to include all files:

1. Install nyc if you don't have it:

   npm install --save-dev nyc

2. Add an .nycrc configuration file or configure it in your package.json:

   {
     "nyc": {
       "all": true,
       "include": ["src/**/*"],
       "exclude": ["**/node_modules/**"]
     }
   }

3. Run your tests with nyc:

   nyc node --test

This ensures that all files matching the include pattern are considered in the report, even if they weren't executed during the test.

---

With Jest:

If you're using Jest, you can include untested files by using the collectCoverageFrom option:

1. Configure jest.config.js:

   module.exports = {
     collectCoverage: true,
     collectCoverageFrom: ["src/**/*.{js,jsx}"],
   };

2. Run Jest:

   npx jest --coverage

This configuration ensures Jest includes all files in the src directory in the coverage report.

---

By following these steps, you should be able to see zero-coverage files in your reports, helping you identify which parts of your project need tests.