Bank Tech Test

How to use and install

1. Fork the repo

2. Access node from the command line

node

3. Require the file in node

const Account = require('./account);

4. Initialise the class

const account = new Account();

5a) To deposit into the account:

account.deposit(1000)

Accounts start with a default balance of 0.

5b) To withdraw from the account:

account.withdraw(500)

Accounts cannot withdraw if the withdrawal amount is greater than the account balance

6. To print the statement:

account.printStatement();

The program will look something like this when it has been run:

Running Tests

Tests are carried out using Jest. They can be carried out from the directory in the command line using:

npm test

Code coverage can be ran using:

npm run coverage

Approaching the problem

I first broke this problem down by thinking of what classes I'd ultimately need. Initially I decided on having two classes: Account and Statement.

Account would be responsible for knowing and showing the balance, being able to deposit and withdraw money and then call the print function.

The print function would then call the Statement class which would format and print the output.

As I was going through the Account class, I realised I should make a transaction class.

The transaction class would represent a single transaction, which would be specified when the class was instantiated along with the balance. The transaction date would be created within the constructor.

Within the transaction class, I had one private method to format the number to 2 decimal places. The other function, showTransaction(), takes the credit or debit, date and balance and stores them in an array which is then joined together separated by || between values.

Moving this functionality to a separate class made it much easier for me to output the date and specific transaction.

After implementing this in the printStatement() function, I decided against keeping a statement class it was one function pulling the data in from the Transaction class and then mapped through in printStatement. I believed that creating a new class would overly complicate what was already a fairly minimal solution.

After some refactoring, I have fixed the mocks in the tests which were initially causing a few problems. I thought I had mocked it correctly, but had gone about it slightly differently to the resources I checked which caused some confusion.

Due to how the Transaction class worked, creating a mock of that class in the Account unit tests proved to be a challenge, especially for tests which required a deposit to be made first prior to a testing the withdrawal. I decided to create an setBalance method, thinking that when bank accounts open you can have funds transferred in as the starting balance. It definitely isn't perfect but without completely re-working the Transaction class I cannot seem to find a solution for testing.

I also added validation for not allowing withdrawals of negative numbers.