Mocha use spec as its default reporter.The spec reporter inherits from Base reporter. It use .epilogue() method of Base for EVENT_RUN_END event.

The method will print the milliseconds, the source code:

Base.consoleLog(fmt, stats.passes || 0, milliseconds(stats.duration));

You can create a custom reporter for mocha.

./reporters/tidy.js:

const Mocha = require('mocha');
const { EVENT_RUN_END, EVENT_TEST_FAIL, EVENT_TEST_PASS } = Mocha.Runner.constants;

class Tidy {
  constructor(runner) {
    const stats = runner.stats;
    runner
      .on(EVENT_TEST_PASS, (test) => {
        console.log(`pass: ${test.fullTitle()}`);
      })
      .on(EVENT_TEST_FAIL, (test, err) => {
        console.log(`fail: ${test.fullTitle()} - error: ${err.message}`);
      })
      .once(EVENT_RUN_END, () => {
        console.log(`end: ${stats.passes}/${stats.passes + stats.failures} ok`);
      });
  }
}

module.exports = Tidy;

Use fullTitle() → {string} to

Return the full title generated by recursively concatenating the parent's full title.

It will give you pass: <test suite title> <test case title> string.

Example test:

const { expect } = require('chai');

describe('description here', () => {
  it('should pass', () => {
    expect(1 + 1).to.be.equal(2);
  });
  it('should fail', () => {
    expect(1 + 1).to.be.equal(3);
  });
});

Output:

⚡  npx mocha --reporter ./reporters/tidy.js /Users/dulin/workspace/github.com/mrdulin/expressjs-research/reporters/index.test.js 
pass: description here should pass
fail: description here should fail - error: expected 2 to equal 3
end: 1/2 ok

While the accepted answer is more sophisticated, I've found a much cheaper way to remove the speeds by increasing the --slow option to a very large number since the speed only appears for slow tests.