unit test mocha Visual Studio Code describe is not defined

Finally!!! After a long search and reading some tutorials and comments I found the solution: the problem was with the config.

Open the test config file and delete the following lines:

            "-u", <<<< delete this line
            "tdd", <<<< delete this line

launch.js

        "version": "0.2.0",
        "configurations": [
            {
                "type": "node",
                "request": "launch",
                "name": "Mocha Tests",
                "program": "${workspaceFolder}/node_modules/mocha/bin/_mocha",
                "args": [
                    "--require", 
                    "ts-node/register",
                    "-u", <<<< delete this line
                    "tdd", <<<< delete this line
                    "--timeout",
                    "999999",
                    "--colors",
                    "${workspaceFolder}/tests/**/*.spec.ts"
                ],
                "internalConsoleOptions": "openOnSessionStart"
            },

Run the test again and it will work.

I've stumbled upon mocha docs here:

Interfaces and UI Switch

TLDR;

--ui, -u switch has two options: bdd and tdd. However, it also states it will be defaulted to bdd when --ui, -u switch is not supplied.

Hence, when you're using --ui tdd switch, you're expected to use TDD interface which provides suite(), test(), suiteSetup(), suiteTeardown(), setup(), and teardown() compared to BDD's describe(), context(), it(), specify(), before(), after(), beforeEach(), and afterEach() approach.

That explains why it screams describe function is not defined.