preloadMocha.ts

interface Options {
  start: (this: Mocha) => any;
  run?: (this: Mocha) => any;
  end?: (this: Mocha) => any;
}

export function preMocha({ start, run, end }: Options) {
  const mocha = require('mocha/lib/mocha');
  const originalRun = mocha.prototype.run;
  mocha.prototype.run = async function preRun(this: Mocha, ...args: any[]) {
    try {
      await start.apply(this);

      run && this.suite.beforeAll(() => run.apply(this));
      end && this.suite.afterAll(() => end.apply(this));

      const returns = originalRun.apply(this, args);
      return returns;
    } catch (error) {
      console.error(error.stack || error);
      process.exit(1);
    }
  };
}