A simple way to enforce that changes to js/ts files require changes to their corresponding test files in legacy code bases where you are trying to expand code coverage over time.

enforce-test-file-changes

#!/usr/bin/env node
const IGNORE_FILES = [];

const filesToParse = JSON.parse(process.env.files);

const filesThatNeedTests = filesToParse.filter((f) => {
  const fileNameArray = f.split('.');
  if (IGNORE_FILES.includes(f)) {
    return false;
  }

  return (
    ['js', 'ts'].includes(fileNameArray.pop()) && fileNameArray.pop() !== 'test'
  );
});

const filesThatAreTests = filesToParse.filter((f) => {
  const fileNameArray = f.split('.');

  return (
    ['js', 'ts'].includes(fileNameArray.pop()) && fileNameArray.pop() === 'test'
  );
});

const untestedFiles = filesThatNeedTests.filter((f) => {
  const fileNameArray = f.split('.');
  const ext = fileNameArray.pop();

  fileNameArray.push('test');
  fileNameArray.push(ext);

  return !filesThatAreTests.includes(`${fileNameArray.join('.')}`);
});

if (untestedFiles.length === 0) {
  process.exit(0);
}

console.log(`
************************************************
It appears you changed a js file but didn't add
or change a test. Please update the tests for
the file in question.

The following files need updated tests:
${untestedFiles.map((f) => `- ${f}\n`).join('')}
************************************************`);
process.exit(1);