Assertion Libary Basic Example (JS Testing)

assertion-library.js

const { sum, subtract } = require('../math'); // const sum = (a, b) => a - b;  const subtract = (a, b) => a - b;
// sum is intentionally wrong to check if error handling is done according to our assertion function

let result, expected;

result = sum(3, 7);
expected = 10;
expect(result).toBe(expected);

result = subtract(7, 3);
expected = 4;
expect(result).toBe(expected);

function expect(actual) {
  return {
    toBe(expected) {
      if (actual !== expected) {
        throw new Error(`${actual} is not equal to ${expected}`);
      }
    },
    toEqual(expected) {},
    toBeGreaterThan(expected) {},
  };
}