Mocha base runner does not emit start event

[karanjitsingh]

Prerequisites

• Checked that your issue hasn't already been filed by cross-referencing issues with the faq label
• Checked next-gen ES issues and syntax problems by using the same environment and/or transpiler configuration without Mocha to ensure it isn't just a feature that actually isn't supported in the environment in question or a bug in your code.
• 'Smoke tested' the code to be tested by running it outside the real test suite to get a better sense of whether the problem is in the code under test, your usage of Mocha, or Mocha itself
• Ensured that there is no discrepancy between the locally and globally installed versions of Mocha. You can find them with: node node_modules/.bin/mocha --version(Local) and mocha --version(Global). We recommend avoiding the use of globally installed Mocha.

Description

Mocha base runner does not emit start event.

Steps to Reproduce

Consider this sample js file

var Mocha = require('mocha');

var mocha = new Mocha({
    reporter: 'base'
});

mocha.addFile("./simple_test.js");

var runner = mocha.run();
runner.on('start', () => {
    console.log("start hook");
});

runner.on('end', () => {
    console.log("end hook");
});

And simple_test.js is

describe("simple suite 1", function () {
    describe("simple suite 2", function () {
        before(function () {
            console.log("before");
        });

        beforeEach(function () {
            console.log("before each");
        });

        it("simple test", function () {
            console.log("test");
            var result = "";
            expect(result).toBe("1");
        });

        afterEach(function () {
            console.log("after each");
        });
        after(function () {
            console.log("after");
        });
    });
});

The output comes out to be

before
before each
test
after each
after
end hook

[outsideris]

Thank you for reporting.
Because this is duplicated of #2753 , I closed it.
The issue should be handled in #2753 .