Coderpad

BankAccount.js

"use strict";

const _ = require('lodash');
const assert = require('assert');
const Mocha = require('mocha')
const mocha = new Mocha();
mocha.suite.emit('pre-require', this, 'solution', mocha);
const sinon = require("sinon");

const OperationType  = {
  Deposit: 'deposit',
  Withdrawal: 'withdrawal'
}

class Operation {
  constructor(operationType, amount, date) {
    this.operationType = operationType;
    this.amount = amount;
    this.date = date;
    Object.freeze(this);
  }

  get value() {
    switch(this.operationType) {
      case OperationType.Deposit:
        return this.amount;
      case OperationType.Withdrawal:
        return -this.amount;
    }
  }
}

class StatementLine {
  constructor(date,operationType, amount, balance) {
    this.date = date;
    this.operationType = operationType;
    this.amount = amount;
    this.balance = balance;
    Object.freeze(this);
  }
}

class Statement {
  lines = [];
  addLine(statementLine) {
    this.lines.push(statementLine);
  }

  #formatDate(date) {
    const [month, day, year]       = [date.getMonth()+1, date.getDate(), date.getFullYear()];
    return `${day}/${month}/${year}`;
  }

  print(printer) {
    printer.print("date || credit || debit || balance");
    [...this.lines].reverse().forEach((line) => {
      if (line.operationType == OperationType.Deposit) {
        printer.print(`${this.#formatDate(line.date)} || ${line.amount} || || ${line.balance}`);
      } else {
        printer.print(`${this.#formatDate(line.date)} || || ${line.amount} || ${line.balance}`);
      }
    })
  }
}

class BankAccount {
  #operations = [];

  get balance() {
    return this.#operations.reduce(
      (previous, current) => previous + current.value,
      0
    );
  }

  deposit(amount, date) {
    this.#operations.push(new Operation(OperationType.Deposit, amount, date));
  }

  withdrawal(amount, date) {
    this.#operations.push(new Operation(OperationType.Withdrawal, amount, date));
  }

  get statement() {
    const statement = new Statement();
    let balance = 0;
    this.#operations.forEach(op => {
      balance += op.value;
      statement.addLine(new StatementLine(op.date, op.operationType, op.amount, balance));
    });
    return statement;
  }

}

describe('Bank Account', function () {
    it('should create an account with starting balance 0', function () {
      assert.equal(new BankAccount().balance, 0);
    });

    it('should make a deposit', function () {
      const bankAccount = new BankAccount();
      bankAccount.deposit(1000, new Date());
      assert.equal(bankAccount.balance, 1000);
    });

    it('should make a withdrawal', function () {
      const bankAccount = new BankAccount();
      bankAccount.deposit(100, new Date());
      bankAccount.withdrawal(80, new Date());
      assert.equal(bankAccount.balance, 20);
    });

    it('should print bank statement', function() {
      const fakePrint = sinon.fake(function(line) { console.log(line); });
      const printer = {
        print: fakePrint
      };

      const bankAccount = new BankAccount();
      bankAccount.deposit(1000, new Date(2012, 0, 10));
      bankAccount.deposit(2000, new Date(2012, 0, 13));
      bankAccount.withdrawal(500, new Date(2012, 0, 14));
      bankAccount.statement.print(printer);

      assert.equal(fakePrint.callCount, 4);
      assert(fakePrint.calledWith("date || credit || debit || balance"));
      assert(fakePrint.calledWith("14/1/2012 || || 500 || 2500"));
      assert(fakePrint.calledWith("13/1/2012 || 2000 || || 3000"));
      assert(fakePrint.calledWith("10/1/2012 || 1000 || || 1000"));

    });

});

mocha.run()

Template.js

"use strict";

const Mocha = require('mocha')
const mocha = new Mocha();
mocha.suite.emit('pre-require', this, 'solution', mocha);

const assert = require('assert');
const sinon = require("sinon");

const _ = require('lodash');


describe('xxx', function () {

    it('should xxx', function () {
      assert.equal(new BankAccount().balance, 0);
    });

});

mocha.run()