Money

class Money {
  private amount: number;
  private currency: string;
 
  constructor(amount: number, currency: string) {
    this.amount = amount;
    this.currency = currency;
  }
 
  equals(other: Money): boolean {
    return this.amount === other.amount && this.currency === other.currency;
  }
 
  toString(): string {
    return `${this.amount} ${this.currency}`;
  }
 
  sum(other: Money): Money {
    if (this.currency !== other.currency) {
      throw new Error("Cannot sum money in different currencies");
    }
    return new Money(this.amount + other.amount, this.currency);
  }
 
  subtract(other: Money): Money {
    if (this.currency !== other.currency) {
      throw new Error("Cannot subtract money in different currencies");
    }
    return new Money(this.amount - other.amount, this.currency);
  }
}
 
// Example usage:
const money1 = new Money(100, "USD");
const money2 = new Money(50, "USD");
console.log(money1.toString()); // Output: "100 USD"
const result = money1.sum(money2);
console.log(result.toString()); // Output: "150 USD"
const result2 = money1.subtract(money2);
console.log(result2.toString()); // Output: "50 USD"

import { Money } from "./money"; // Import the Money class
 
describe("Money", () => {
  describe("constructor", () => {
    it("should create a Money instance with valid amount and currency", () => {
      const money = new Money(100, "USD");
      expect(money).toBeDefined();
    });
 
    it("should throw an error for an invalid amount", () => {
      expect(() => new Money(-100, "USD")).toThrow();
    });
 
    it("should throw an error for an invalid currency", () => {
      expect(() => new Money(100, "XYZ")).toThrow();
    });
  });
 
  describe("equals", () => {
    it("should return true when comparing two Money instances with the same amount and currency", () => {
      const money1 = new Money(100, "USD");
      const money2 = new Money(100, "USD");
      expect(money1.equals(money2)).toBe(true);
    });
 
    it("should return false when comparing two Money instances with different amounts", () => {
      const money1 = new Money(100, "USD");
      const money2 = new Money(200, "USD");
      expect(money1.equals(money2)).toBe(false);
    });
 
    it("should return false when comparing two Money instances with different currencies", () => {
      const money1 = new Money(100, "USD");
      const money2 = new Money(100, "EUR");
      expect(money1.equals(money2)).toBe(false);
    });
  });
 
  describe("toString", () => {
    it("should return the string representation of the Money", () => {
      const money = new Money(100, "USD");
      expect(money.toString()).toBe("100 USD");
    });
  });
 
  describe("sum", () => {
    it("should correctly sum two Money instances with the same currency", () => {
      const money1 = new Money(100, "USD");
      const money2 = new Money(50, "USD");
      const result = money1.sum(money2);
      expect(result.toString()).toBe("150 USD");
    });
 
    it("should throw an error when trying to sum Money instances with different currencies", () => {
      const money1 = new Money(100, "USD");
      const money2 = new Money(50, "EUR");
      expect(() => money1.sum(money2)).toThrow();
    });
  });
 
  describe("subtract", () => {
    it("should correctly subtract two Money instances with the same currency", () => {
      const money1 = new Money(100, "USD");
      const money2 = new Money(50, "USD");
      const result = money1.subtract(money2);
      expect(result.toString()).toBe("50 USD");
    });
 
    it("should throw an error when trying to subtract Money instances with different currencies", () => {
      const money1 = new Money(100, "USD");
      const money2 = new Money(50, "EUR");
      expect(() => money1.subtract(money2)).toThrow();
    });
  });
});