For a practice tech test, I have been tasked to create a Bank Account system that allows people to deposit money, withdraw money and print their bank statement.
The program will be ran in Node but will not need to have a Command Line Interface. The focus of the project is to practice OO design and TDD skills and the project will be completed solo with self-reviews done to reflect and improve upon my own code.
Clone this repository using git clone https://github.com/mcsuGH/Bank-Tech-Test.git
Run npm install to install any dependencies then run npm run test to run the tests for the code which will also give you the code coverage.
To use the program, whilst in the main directory in the terminal, run node to open up Node, then use the command const BankAccount = require('./lib/bankAccount'). Create a new account using const account = new BankAccount(); then use the functions account.deposit(num) and account.withdraw(num) with num being the amount in GBP (entering 1 is equivalent to £1). After finishing your transactions, use the command account.printStatement() to display your bank statement inside your terminal.
Example of my code running:
- 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).
Given a client makes a deposit of 1000 on 10-01-2023
And a deposit of 2000 on 13-01-2023
And a withdrawal of 500 on 14-01-2023
When she prints her bank statement
Then 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
As a Client,
So that my money can be stored safely,
I would like to be able to deposit my money
As a Client,
So that I can use my money,
I would like to be able to withdraw my money
As a Client,
So that I can check the money in my account,
I would like to be able to print a bank statement
As a Client,
So that I can see what happened to my money,
The statement should include the dates of when deposits and withdrawals were made aswell as the balance remaining
As a Client,
So that I can easily check the latest updates on my account,
The statement should show the most recent actions first
Possible Edge Cases:
As the Bank,
So that my customers do not overdraft,
I would like the customers to not be able to withdraw more money than they have
As the Bank,
So that my customers have valid balances,
I would like the customers to only be able to put in valid user inputs
I initially started with writing all the code inside the same code file but it became apparent early on from writing tests that a Transaction class would be needed so I ended up with two classes - Bank Account class and Transaction class. I considered creating a Statement class too to print out the bank statements but initially I thought it didn't seem necessary as the method used to print it still seemed concise and there was no need for any variables for printing out the statement so there didn't seem to be a need for splitting it off into a new class. After self reviewing my code, I decided to make the Statement class after all to abide by SRP better.
I considered a few edge cases that were not part of the spec such as not allowing overdrafts (which led to the introduction of a balance check when withdrawing money) and also to check that when depositing and withdrawing, the amount would be a valid monetary amount. I raised errors according to these situations so that accounts can still keep working as per normal even after a action that would raise an error - previously, these actions could break the program (such as when entering a string in place of the amount, the balance would become NaN, or Not a Number). These edge cases have both been tested and accounted for in my program as can be seen above in the pictures.
The Transaction class I originally made ended up being redundant after making the TransactionHistory class and as a result, I removed the Transaction class and instead just created objects within the TransactionHistory class similar to what Transaction was. This allowed me to reduce the complexity of the program and reduce the number of classes from 5 down to 4.
I used Jest for testing, Prettier to format my code and attempted to use ESLint as a linter - however, there would be many clashes between ESLint and Prettier (for example, ESLint would raise problems for using "" instead of '', but Prettier would use ""). ESLint also would raise problems with a few other issues that would end up breaking the tests/code (such as using !== instead of != for my inequality when checking decimal places). As a result, I opted against using ESLint to lint my code and just stuck with using Prettier to format it instead.
https://stackoverflow.com/questions/49096093/how-do-i-test-a-jest-console-log
https://jestjs.io/docs/es6-class-mocks
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/typeof
https://www.npmjs.com/package/mockdate
used the above to mock console.log
used the above to mock Transaction class
used the above to check for valid input on numbers
used the above to mock date on test