Extend Jest in TS and fix: ES2015 module syntax, Augmentations for the global scope (https://www.bramadams.dev/projects/jest-ts-extentions)

extend-jest.ts

export {}

// https://jestjs.io/docs/expect#expectextendmatchers
declare global {
  // eslint-disable-next-line @typescript-eslint/no-namespace
    namespace jest {
      interface Matchers<R> {
        toBeWithinRange(a: number, b: number): R;
      }
    }
}

expect.extend({
  toBeWithinRange(received, floor, ceiling) {
    const pass = received >= floor && received <= ceiling;
    if (pass) {
      return {
        message: () =>
          `expected ${received} not to be within range ${floor} - ${ceiling}`,
        pass: true,
      };
    } else {
      return {
        message: () =>
          `expected ${received} to be within range ${floor} - ${ceiling}`,
        pass: false,
      };
    }
  },
});