simple.test.ts

import { checkNumber } from "../checkNumber";
import * as chai from "chai";

const expect = chai.expect;

/**
 * Takes in a function and checks for error
 * @param {Function} method - The function to check
 * @param {any[]} params - The array of function parameters
 * @param {string} message - Optional message to match with error message
 */
const expectThrowsAsync = async (
  method: Function,
  params: any[],
  message?: string
) => {
  let err = null;
  try {
    await method(...params);
  } catch (error) {
    err = error;
  }
  if (message) {
    expect(err.message).to.be.equal(message);
  } else {
    expect(err).to.be.an("Error");
  }
};

describe("Simple Number Test", function () {
  // Will Pass
  it("Check Positive Number", async function () {
    await checkNumber(10);
  });

  // Will Pass
  it("Check Negative Number without message", async function () {
    await expectThrowsAsync(checkNumber, [-50]);
  });

  // Will Pass
  it("Check Negative Number with the right message", async function () {
    await expectThrowsAsync(
      checkNumber,
      [-45],
      "Negative numbers are not accepted"
    );
  });

  // Will Fail
  it("Check Negative Number with the wrong message", async function () {
    await expectThrowsAsync(
      checkNumber,
      [-45],
      "Some other error message which will cause the test to fail"
    );
  });
});