NodeJS Test Runner Dry Run/Discovery?

[JustinGrote]

CC @targos

Is it possible programattically to discover what NodeJS tests are available but not actually run them?

I'm working on a Visual Studio Code extension to integrate the node test runner into the Testing API, however I can't really see a way to currently "dry run" or "discover" tests without actually executing them.

[dlenroc]

Without running tests, you'll likely need to parse the source code of the tests, much like the nodejs-testing VSCode extension does.

If you're okay with a dry run approach that skips tests but runs everything outside of them.

import { resolve } from 'node:path';
import { run } from 'node:test';

const events = run({
  files: [resolve('sample.test.js')],
  testNamePatterns: /^(?=a)b/, // skip all tests since there are no matches
});

const tests = [];
for await (const event of events) {
  if (event.type !== 'test:start') continue;
  tests.push(event.data);
}

console.log(tests);
// [
//   {
//     nesting: 0,
//     name: 'test 1',
//     line: 3,
//     column: 1,
//     file: 'file:///.../sample.test.js'
//   },
//   {
//     nesting: 0,
//     name: 'test 2',
//     line: 5,
//     column: 1,
//     file: 'file:///.../sample.test.js'
//   }
// ]

Note: same can be achieved using --test-name-pattern and --test-reporter cli arguments to skip tests and collect results.