Augmenting the Context type used by Mocha in beforeEach, it, etc.

augmentations.d.ts

import { Erc20 } from "../typechain/Erc20";

declare module "mocha" {
  export interface Context {
    token: Token;
  }
}

test.ts

import { deployContract } from "ethereum-waffle";

import Erc20Artifact from "../../artifacts/Erc20.json";

import { Erc20 } from "../../typechain/Erc20";

  describe("Token", function () {
    beforeEach(async function() {
      const decimals: number = 18;
      const name: string = "My Token";
      const symbol: string = "TKN";
      this.token = (await deployContract(deployer, Erc20Artifact, [name, symbol, decimals])) as Erc20;
    });
  
    it("should test something", async function() {
      // this.token has auto-completion here!
    });
  });