singleSubtestTests.js

const fs = require('fs');

const args = process.argv.slice(2)

const singleSubtestTests = new Set();

for (const reportPath of args) {
  const report = JSON.parse(fs.readFileSync(reportPath));

  for (const result of report.results) {
    if (result.subtests && result.subtests.length === 1) {
      singleSubtestTests.add(result.test);
    }
  }
}

console.log(singleSubtestTests.size);