unable to add functions to `this` (Context)

Current behavior

Adding functions to this (which is a Mocha Context) yields an error.

Desired behavior

I want to add functions to have them on this in tests, so I can do e.g.

describe('my spec', () => {
  it('should work', function () {
    this.sayHelloWorld();
  })
})

Test code to reproduce

In an empty folder I call

yarn add cypress
yarn cypress open

so that default config files are created. It also creates a sample test in cypress/e2e/spec.cy.js.

I can run the sample test without problem. But if I add

import { Context } from "mocha";

to cypress/support/e2e.js I get

Error: Webpack Compilation Error
./cypress/support/e2e.js
Module not found: Error: Can't resolve 'mocha' in '...\support'
resolve 'mocha' in '...\support'
  Parsed request is a module

So I installed Mocha, the same version which is in devDependencies of Cypress (see package.json):

yarn add mocha@3.5.3

My package.json now looks like this:

{
  "dependencies": {
    "cypress": "^10.4.0",
    "mocha": "3.5.3"
  }
}

Now that import line passes. But this fails:

import { Context } from "mocha";

Context.prototype.sayHelloWorld = () => console.log("hello world");

Error:

> Cannot read properties of undefined (reading 'prototype')

Why is that? In comparison adding something to String.prototype works.

And it also works in Mocha without Cypress. In another empty folder:

yarn add mocha@3.5.3

And in test/test.js:

const { Context } = require("mocha");
it("works", function () {
  Context.prototype.sayHelloWorld = () => console.log("hello world");
  this.sayHelloWorld();
});

Now yarn mocha works (says hello world).

Why does this work in Mocha but not in Cypress?

Cypress Version

10.4.0

Other

No response

[iomedico-beyer]

But simply adding my stuff to this in before did the trick. Thank you very much! 💚 Looks like I still have a lot to learn about JavaScript and TypeScript …

I found another solution:

Mocha.Context.prototype.sayHelloWorld = function () {
    cy.log('hello world');
};

(no import)

[rockindahizzy]

Hey @iomedico-beyer, thanks for the additional info!

I made a small repo showcasing how you might accomplish this pattern here. The specific changes I made can be seen in this commit.

Let me know if that helps!