Coverage

nyc

Standard setup

From the README:

package.json

  {
    "scripts": {
      "test": "mocha",
      "coverage": "nyc npm test"
    }
  }

.gitignore
```
  .nyc_output/
  coverage/
```

Then run:

$ npm run coverage

Docs example setup

From Combining reports from multiple runs.

{
  "scripts": {
    "cover:unit": "nyc --silent npm run test:unit",
    "cover:integration": "nyc --silent --no-clean npm run test:integration",
    "cover:report": "nyc report --reporter=lcov --reporter=text",
    "cover": "npm run cover:unit && npm run cover:integration && npm run cover:report"
  }
}

Auto Commit Message project setup

From package.json

This project compiles TypeScript to out and runs against there. But you could use some other test directory.

package.json

  {
    "scripts": {
      "test:unit": "cd out && mocha --recursive",
      "test": "npm run test:unit",
      "test:coverage": "nyc npm test",
      "test:report": "nyc report --reporter=lcov"
    },

    "devDependencies": {
      "mocha": "^8.3.2",
      "nyc": "^15.1.0"
  }

And set up .gitignore as in previous example.

Then run:

Tests with no coverage.
```
  $ npm run test:coverage
```
Tests, followed by CLI coverage report.
```
  $ npm run test:coverage
```
Create HTML report.
```
  $ npm run test:report
```

Sample CLI report:

----------------------|---------|----------|---------|---------|-------------------
File                  | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------------------|---------|----------|---------|---------|-------------------
All files             |   91.63 |    87.85 |   88.24 |   91.28 |                   
 src                  |   62.16 |    33.33 |   44.44 |   62.16 |                   
  prepareCommitMsg.ts |   62.16 |    33.33 |   44.44 |   62.16 | 75-126,139-142    
 src/generate         |      97 |    96.83 |   95.24 |   96.91 |        
 ...

Configuration

See Common Configuration Options

Or see output of:

$ npx nyc --help

For config filenames see Configuration files in the docs.

Example of CLI config usage:

… the following command executes ava, and indicates to nyc that it should output both an lcov (lcov.info + html report) and a text-summary coverage report.

$ nyc --reporter=lcov --reporter=text-summary ava

You might like to add the--silent flag.

Check coverage

Fail a check if coverage drops below any thresholds.

Check whether the JSON in nyc’s output folder meets the thresholds provided

$ nyc check-coverage --lines 95

You can pass arguments as --lines, --statements, --functions and --branches.

The default is to fail is any of those drop below 100%. You might like to be less strict at 80%.

From the CLI help for that subcommand:

Flag	Description	Default
`--branches`	what % of branches must be covered?	`0`
`--functions`	what % of functions must be covered?	`0`
`--lines`	what % of lines must be covered?	`90`
`--statements`	what % of statements must be covered?	`0`

You can also set high and low watermarks.

Istanbul

This is deprecated. Using nyc instead.

On installing Istanbul:

npm WARN deprecated istanbul@0.4.5: This module is no longer maintained, try this instead:
npm WARN deprecated   npm i nyc

Jest

$ npm i -D jest

Set up your npm test:coverage command to do this:

$ jest --coverage

.gitignore
```
  coverage/
```

Then run:

$ npm test:coverage

Collect coverage

Note use of collect coverage setting. Rather than only collecting coverage metrics for scripts and specs that run, include untested files as part of the coverage stats.

A solution from issue - Jest is “stuck” on only generating coverage for tested files, instead of all files #8310.

{
  "jest": {
    "collectCoverageFrom": [
      "src/**/*.js"
    ],
    "collectCoverage": true,
    
    "verbose": true,
    "testTimeout": 30000,
    "roots": [
      "<rootDir>/tests",
      "<rootDir>/src"
    ],
    "testRegex": "((\\.|/*.)(test))\\.js?$",
    
    "moduleFileExtensions": [
      "ts",
      "tsx",
      "js",
      "jsx",
      "json",
      "node"
    ]
  }  
}

Vue and Jest

Note that from the Vue CLI help, all jest command line options are supported.

package.json

  {
    "scripts": {
      "test:coverage": "vue-cli-service test:unit --detectOpenHandles --coverage",
    }
  }

.gitignore
```
  coverage/
```

Then run:

$ npm test
$ # OR
$ yarn test