What is the reason for getting "Error: not supported" when trying to run chai mocha tests in GitLab Ci/Cd pipeline?

I am trying to run a very simple mocha test in a GitLab Ci/Cd pipeline.

My application uses nodejs, express and typescript.

The directory structure looks like this:

  - root
     - backend
        - src
           - index.ts
           - tests
             - chai
               - index.ts
        - Dockerfile
        - nodedemon
        - package.json
        - package_lock.json
        - tsconfig.json
     - .gitlab-ci.yml
     - docker-compose.yml

With src/index.ts creating the express server.

chai/index.ts looks like this:

    import chaiHttp from "chai-http";
    import chai from "chai";
    import {app} from "../../index";
    
    
    chai.use(chaiHttp);
    
    // Test base route to return string
    describe("Base Route Test", () => {
        it(`should return a html file`, () => {
            return chai.request(app).get("/")
                .then(res  => {
                    chai.expect(res).to.be.html
                })
        })
    })

The nodemon file looks like this:

    {
      "watch": ["src"],
      "ext": ".ts",
      "ignore": [],
      "exec": "ts-node ./src/index.ts"
    }

Dockerfile:

    FROM node:16.13.0
    
    WORKDIR /usr/src/app
    
    COPY package*.json ./
    
        RUN npm install
        COPY . .
        EXPOSE 8008
        RUN npm run build
        ENTRYPOINT ["npm", "run", "start"]

docker-compose.yml:

    
        version: '3.0'
        services:
          mongo:
            image: mongo
            container_name: cargonaut_mongo
            ports:
              - "27017:27017"
          node:
            build: ./backend
            container_name: cargonaut
            ports:
              - "8008:8008"
            depends_on:
              - mongo
            environment:
              - "NODE_ENV=${NODE_ENV}"

and package.json (gitlab-instance and name censored using --):

    {
        "name": "cargonaut",
        "version": "1.0.0",
        "description": "",
        "main": "index.js",
        "scripts": {
            "start": "nodemon",
            "build": "npx tsc",
            "test": "mocha -r ts-node/register src/tests/chai/index.ts"
        },
        "repository": {
            "type": "git",
            "url": "git@-------:-----/cargonaut.git"
        },
        "author": "",
        "license": "ISC",
        "devDependencies": {
            "@types/config": "^0.0.41",
            "@types/cors": "^2.8.12",
            "@types/express": "^4.17.13",
            "@types/mocha": "^9.1.1",
            "@typescript-eslint/eslint-plugin": "^5.27.0",
            "@typescript-eslint/parser": "^5.27.0",
            "eslint": "^8.18.0",
            "nodemon": "^2.0.16",
            "ts-node": "^10.8.0",
            "typescript": "^4.7.2"
        },
        "dependencies": {
            "@babel/types": "^7.18.4",
            "@types/chai": "^4.3.1",
            "@types/express-session": "^1.17.4",
            "@types/node": "^18.0.0",
            "body-parser": "^1.20.0",
            "chai": "^4.3.6",
            "chai-http": "^4.3.0",
            "config": "^3.3.7",
            "cors": "^2.8.5",
            "express": "^4.18.1",
            "express-session": "^1.17.3",
            "json5": "^2.2.1",
            "mocha": "^10.0.0",
            "mongoose": "^6.4.0"
        }
    }

And finally, the gitlab-ci.yml:

    docker build:
        stage: build
        tags:
            - npm
        before_script:
            - cd backend
            - npm install
        script:
            - NODE_ENV=test_docker_free npm run test

This commands work on my computer, but if I push to my repo, the pipeline fails with the following output:

    $ NODE_ENV=test_docker_free npm run test
    npm info it worked if it ends with ok
    npm info using npm@6.9.0
    npm info using node@v10.16.1
    npm info lifecycle cargonaut@1.0.0~pretest: cargonaut@1.0.0
    npm info lifecycle cargonaut@1.0.0~test: cargonaut@1.0.0
    > cargonaut@1.0.0 test /builds/----/cargonaut/backend
    > mocha -r ts-node/register src/tests/chai/index.ts
    ✖ ERROR: Error: Not supported
        at formattedImport (/builds/----/cargonaut/backend/node_modules/mocha/lib/nodejs/esm-utils.js:30:3)
        at exports.requireOrImport (/builds/----/cargonaut/backend/node_modules/mocha/lib/nodejs/esm-utils.js:38:34)
        at exports.handleRequires (/builds/----/cargonaut/backend/node_modules/mocha/lib/cli/run-helpers.js:94:34)
        at process._tickCallback (internal/process/next_tick.js:68:7)
        at Function.Module.runMain (internal/modules/cjs/loader.js:834:11)
        at startup (internal/bootstrap/node.js:283:19)
        at bootstrapNodeJSCore (internal/bootstrap/node.js:622:3)
    npm info lifecycle cargonaut@1.0.0~test: Failed to exec test script
    npm ERR! code ELIFECYCLE
    npm ERR! errno 1
    npm ERR! cargonaut@1.0.0 test: mocha -r ts-node/register src/tests/chai/index.ts
    npm ERR! Exit status 1
    npm ERR! 
    npm ERR! Failed at the cargonaut@1.0.0 test script.
    npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
    npm timing npm Completed in 469ms
    npm ERR! A complete log of this run can be found in:
    npm ERR!     /root/.npm/_logs/2022-06-26T09_56_58_783Z-debug.log
    Cleaning up project directory and file based variables 00:01
    ERROR: Job failed: exit code 1

I found this bug report: https://github.com/mochajs/mocha/issues/4652 but I am not sure if it is relevant in my case, since I use mocha 10.00 and node v16.13.0 and the issue seems to affect older versions.

So what is the reason for the error? Is there a way to fix it?