jest-coverage-ratchet

Raises jest's minimum coverage thresholds (per category) if current coverage is higher.

What does it do?

Lets say you have some jest coverage thresholds set in the package.json for your project at the following values:

{
  "branches": 30,
  "functions": 30,
  "lines": 30,
  "statements": 50,
}

then you get inspired one day and write lots of tests. Now your actual coverage summary might look like this:

{
  "branches": 50,
  "functions": 60,
  "lines": 77,
  "statements": 50,
}

Great 🌸‼ Except you'd really like your accomplishment to set the new standard for test coverage in this project. jest-coverage-ratchet just does that automatically by looking at your current coverage summary, comparing it to your specified coverage thresholds, and updating the minimum for any threshold that is higher in the summary.

So given the previous values, running this script will update your coverage thresholds specified in the jest key of package.json to the following values:

{
  "branches": 50,
  "functions": 60,
  "lines": 77,
  "statements": 50,
}

Installation

Just add as a dev dependency to your project like

npm install --save-dev jest-coverage-ratchet

or

yarn add --dev jest-coverage-ratchet

I recommend then using the binary jest-coverage-ratchet as part of a prepush hook.

Assumptions

I know what happens when you assume, but jest-coverage-ratchet makes the following assumptions about your project.

• jest has been run for project at least once with --coverage so that there is a valid file at the path ./coverage/coverage-summary.json (alternatively pass a path with --coverageSummaryPath of ./your/path/to/coverage-summary.json)
• jest configuration object is present in the package.json that specifies at least:
  • coverage thresholds (alternatively pass a path with --configPath of ./your/path/to/jest.config.json)
  • 'json-summary' in your jest config's reporters list like so:

  {
    // ...
    "jest": {
      "coverageReporters": [
        "json-summary"
      ],
      "coverageThreshold": {
        "global": {
          "branches": Number,
          "functions": Number,
          "lines": Number,
          "statements": Number,
        }
      }
    },
    // ...
  }

Should this tool support things like piping the coverage data in as an argument? Of course it should. If you want to build that and send a PR I will be all smiles 😀✨. If not then you probably see me do it eventually.

Usage example

After all assumptions are satisfied. Set scripts in the package.json...

"scripts": {
    "jest": "./node_modules/.bin/jest",
    "ratchet": "./node_modules/.bin/jest-coverage-ratchet",
    "test": "npm run jest && npm run ratchet && rm -rf coverage"

...run...

npm test

...and get it!

new coverage thresholds:
{
  "lines": Number,
  "statements": Number,
  "functions": Number,
  "branches": Number
}

Questions?

Just submit an issue or a PR, I'm no elitist.