in packages/web-scripts/src/Tasks/TestTask.ts [39:52]
export function testTask(task: TestTaskDesc): SpawnSyncReturns<Buffer> {
// `coverageDirectory` is necessary because the root is `src`
const cmd = 'npx';
const config = task.config || getJestConfig();
const args = [
'--no-install',
'jest',
...(config ? ['--config', config] : []),
...task.restOptions,
];
dbg('npx args %o', args);
return spawn.sync(cmd, args, { stdio: 'inherit' });
}