Getting an error saying Set doesn't have new (as of 2023) methods, uncertain where problem is

[paceaux]

I've got this project which started life as JS, was then converted to TS. I'm trying to update one file to use new methods that are are on the Set object.

I have no problem building. The compiled code runs as expected.

But when I run my unit tests, I get an error: "TypeError: set.union is not a function".

(My node version is 20).

This is my jest.config.js

module.exports = {
  testMatch: [
    '(/test/.*|(\\.|/)(test|spec))\\.[jt]sx?$',
    '**/?(*.)+(spec|test).[tj]s?(x)',
  ],
  transform: {
    '^.+\\.[t|j]sx?$': 'babel-jest',
    '^.+.tsx?$': [
      'ts-jest',
      {
        tsconfig: 'tsconfig.json',
      },
    ],
  },
  testEnvironment: 'node',
};

And this is my tsconfig

{
  "compilerOptions": {
    "declaration": true,
    "declarationMap": true,
    "inlineSources": true,
    "target": "ES2018",
    "module": "commonjs",
    "moduleResolution": "node",
    "esModuleInterop": true,
    "outDir": "dist",
    "strict": true,
    "allowJs": true,
    "sourceMap": true,
    "lib": [
      "ESNext"
    ],
  },
  "include": [
    "src/**/*.ts",
    "typings/**/*.d.ts",
  ],
  "paths": {
    "~*": ["./src/*"]
  },
  "exclude": [
    "node_modules/**/*.*",
    "test/**/*.*",
    "**/*.spec.ts",
  ],
  "declaration": true,
}

And this is my babel config

{
    "presets" : [
        [
            "@babel/preset-env",
            {
                "targets" : {
                    "node" : "20",
                    "browsers" : [
                        "> 1%",
                        "last 2 node versions",
                        "ie > 11"
                    ]
                },
                "useBuiltIns" : "usage",
                "corejs" : 3
            }
        ],
        "@babel/preset-typescript"
    ],
    "sourceType": "module",
    "sourceMap": true
}

My node version is 20, also. I don't understand why something doesn't recognize that Set() has new methods. I realize that Set() doesn't have new methods until Node 22. So I'm guessing this somehow is tying back to Babel. How can I get Babel to correctly polyfill these methods for Jest?