create-lite-jest-runner/src/index.ts

A lightweight Jest runner creator

import { SerializableError, TestResult } from "@jest/test-result";
import type { Config } from "@jest/types";
import type * as JestRunner from "jest-runner";
import pLimit from "p-limit";

interface RunnerOptions {
  testPath: string;
  context: JestRunner.Test["context"];
}

type Runner = (options: RunnerOptions) => Promise<TestResult>;

export default (run: Runner) =>
  class LiteTestRunner {
    constructor(
      public readonly _globalConfig: Config.GlobalConfig,
      public readonly _context: JestRunner.TestRunnerContext = {}
    ) {
      this._globalConfig = _globalConfig;
      this._context = _context;
    }

    async runTests(
      tests: Array<JestRunner.Test>,
      _: JestRunner.TestWatcher,
      onStart: JestRunner.OnTestStart,
      onResult: JestRunner.OnTestSuccess,
      onFailure: JestRunner.OnTestFailure
    ): Promise<void> {
      const limit = pLimit(this._globalConfig.maxWorkers);

      const promises = tests.map((test) =>
        limit(async () => {
          await onStart(test);
          try {
            const result = await run({
              testPath: test.path,
              context: test.context,
            });
            await onResult(test, result);
          } catch (error) {
            await onFailure(test, error as SerializableError);
          }
        })
      );

      await Promise.all(promises);
    }
  };

export { pass, fail } from "./results.js";