hardhat-template/test/Greeter.behavior.ts

import { Signer } from "@ethersproject/abstract-signer";
import { expect } from "chai";

export function shouldBehaveLikeGreeter(_signers: Signer[]): void {
  it("should return the new greeting once it's changed", async function () {
    expect(await this.greeter.greet()).to.equal("Hello, world!");

    await this.greeter.setGreeting("Hola, mundo!");
    expect(await this.greeter.greet()).to.equal("Hola, mundo!");
  });
}