Bank tech test

Quick start

clone this repository
type bundle install to install dependencies

Full details of dependencies are under the heading 'Dependencies' at the bottom of this page.

Requirements

These requirements were provided in the exercise

You should be able to interact with your code via a REPL like IRB or Node. (You don't need to implement a command line interface that takes input from STDIN.)
Deposits, withdrawal.
Account statement (date, amount, balance) printing.
Data can be kept in memory (it doesn't need to be stored to a database or anything).

Acceptance criteria

A client makes:

a deposit of 1000 on 10-01-2023
a deposit of 2000 on 13-01-2023
a withdrawal of 500 on 14-01-2023

When she prints her bank statement she would see:

date || credit || debit || balance
14/01/2023 || || 500.00 || 2500.00
13/01/2023 || 2000.00 || || 3000.00
10/01/2023 || 1000.00 || || 1000.00

Design overview

I have chosen to code this tech-test in ruby.

A persons money is held in a bank account where they can deposit, withdraw, and view statements.

Bank class will be used to coordinate all activities
BankAccount class handles transactions
Statement class will handles statement viewing

This basic structure gives:

Function	Class name
Model	BankAccount
Controller	Bank
View	Statement

External interaction is via the controller

Bank class

# class name
class Bank
  def initialize
    BankAccount.new
    Statement.new
  end
end

These methods provide the required functionality:

# returns statement in a format that can be printed
# takes no arguments
def show_statement
end

# desposit into the bank account
def deposit(amount) # amount is a number
end

# withdraw from the bank account
def withdraw(amount) # amount is a number
end

BankAccount class

class BankAccount
end

These methods interact with Bank class

def transact(amount)
  # move money in or out of the bank account
end

def all_transactions
  # return all account transactions
end

Statement class

class Statement
end

This method interacts with Bank class

def create_statement(bank_account)
  # return statement information for a given BankAccount in a printable format
end

Input / Output

Assumed behaviour is adopted where the specification does not give explicit guidance

# create bank account and view statement with no transactions
my_bank = Bank.new
my_bank.show_statement => date || credit || debit || balance

# create bank account, add 200 and view statement
my_bank = Bank.new
my_bank.deposit(200) => 200 will be credited to account
my_bank.show_statement =>
date || credit || debit || balance
dd/mm/yyyy || 200.00 || || 200.00

# create bank account, add 200, withdraw 50 and view statement
my_bank = Bank.new
my_bank.deposit(200) => 200 will be credited to account
my_bank.withdraw(50) => 50 will be debited from account
my_bank.show_statement =>
date || credit || debit || balance
dd/mm/yyyy || || 50.00 || 150.00
dd/mm/yyyy || 200.00 || || 200.00

# deposit / withdrawal
my_bank = Bank.new
my_bank.deposit("loadsa money") => Error: 'method takes a positive number as an argument'
my_bank.withdraw("loadsa money") => Error: 'method takes a positive number as an argument'

# round deposits / withdrawals to 2 decimal places
my_bank = Bank.new
my_bank.deposit(3.1415927) => 3.1415927 will be credited to account
my_bank.show_statement =>
date || credit || debit || balance
dd/mm/yyyy || 3.14 || || 3.14

# allow account to go overdrawn - no overdraft limit
my_bank = Bank.new
my_bank.withdraw(50) => 50 will be debited from account
my_bank.show_statement =>
date || credit || debit || balance
dd/mm/yyyy || || 50.00 || -50.00

# withdraw / deposit blank (no args)
my_bank = Bank.new
my_bank.withdraw => 'Error: wrong number of arguments (given 0, expected 1)'

# withdraw / deposit zero
my_bank = Bank.new
my_bank.withdraw(0) => => Error: 'method takes a positive number as an argument'

# withdraw / deposit calculation in args
my_bank = Bank.new
my_bank.deposit(50 + 150) => deposits 200
my_bank.show_statement =>
date || credit || debit || balance
dd/mm/yyyy || 200.00 || || 200.00

# transaction date
my_bank = Bank.new(BankAccount.new(0, mock_time))
expect(mock_time).to receive(:now).and_return(Time.new(2023, 1, 10))
my_bank.deposit(200) => 200 will be credited to account
my_bank.show_statement =>
date || credit || debit || balance
10/01/2023 || 200.00 || || 200.00

# sort in reverse date order NOT transaction entry order
my_bank = Bank.new(BankAccount.new(0, mock_time))
expect(mock_time).to receive(:now).and_return(Time.new(2023, 1, 10))
my_account.deposit(200) => 200 will be credited to account
expect(mock_time).to receive(:now).and_return(Time.new(2023, 1, 8))
my_account.withdraw(50) => 50 will be debited from account
my_account.show_statement =>
date || credit || debit || balance
10/01/2023 || 200.00 || || 150.00
08/01/2023 || || 50.00 || -50.00

Example use

This example shows how to use the methods, and their responses when interacting with the Bank class using irb:

3.0.0 :001 > require('./lib/bank')
 => true 
3.0.0 :002 > my_bank = Bank.new
 => #<Bank:0x00007fa97a146600 @bank_account=#<BankAccount:0x00007fa97a1465b0 @time=Time, @opening_balance=0, @transactions=[]>, @statement=#<Statement:0x00007fa97a146330>> 
3.0.0 :003 > my_bank.deposit(1000)
 => [2022-09-21 15:36:13.728527 +0100, 1000] 
3.0.0 :004 > my_bank.deposit(2000)
 => [2022-09-21 15:36:30.184626 +0100, 2000] 
3.0.0 :005 > my_bank.withdraw(500)
 => [2022-09-21 15:36:35.673944 +0100, -500] 
3.0.0 :006 > print(my_bank.show_statement)
date || credit || debit || balance
21/09/2022 || || 500.00 || 2500.00
21/09/2022 || 2000.00 || || 3000.00
21/09/2022 || 1000.00 || || 1000.00 => nil

Dependencies

This project uses:

rspec for testing
simplecov for test coverage
rubocop for linting

Gemfile

source "https://rubygems.org"

group :test do
  gem 'rspec', "~> 3.11"
  gem 'simplecov', require: false
  gem 'simplecov-console', require: false
end

group :development, :test do
  gem 'rubocop', '1.36'
end

stephenfletchtek/bank-tech-test