Bank tech test

Contents

The assignment

Requirements

How to install

How to run

How to run tests

Notes from the Author

The assignment

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

Requirements

• You should be able to interact with your code via a REPL.
• 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).

How to install

Once you have cloned the repo cd into the directory then install node modules:

npm install

How to run

An example use case of the code is setup in the index.js file. To execute this code run:

node index.js

You should see the example output from the assignment appear in the terminal.

It is also setup to be run in the Node REPL.

node;
const { Account, Display } = require('./index.js');

You now have access to the two classes.

How to run tests

[A note on tests] GitHub actions were setup to run a Node.js build and run the tests. These were successful until a date formatter was introduced. As I am local to the UK and the GitHub servers are located in the US, the date and month are reversed, thus breaking the tests. Despite setting the timezone to GMT in /gitworkflows and the local region to the UK in .toLocalDateString("en-GB"), GitHub runners do not have UK local outputs built in.

I have not removed this badge as it shows use of CI/CD and I would like to find a solution to this GitHub issue.

SOLUTION - I have updated the tests on Display.test.js to adapt the date string to the region they are run in.

To run the tests locally, make sure you are in the root directory of the app and run:

npm run test

Test Coverage

There is full test coverage. To observe this run the script:

npm run coverage

Notes from the author

The initial plan for development is available to view.

• The ongoing balance was added to transaction objects to avoid:
  • numeric logic being added to the Display class
  • to create a function aiming for the assignment requirements first and foremost
• Effort was taken on encapsulation. The currentBalance in the constructor isn't made available via a method, however constructor functions cannot be made private and so can be accessed directly. One last refactor was to remove the constructor and use #currentBalance. Now this is not accessible.
• This makes this app work for non-malicious, normal use.
• The listTransactions() function gives access to the transactions array, which contains references to the transaction objects. This means you can access them and change them.
• To combat this I have implemented Object.freeze() when creating these objects
• Time was spent finding an appropriate jest matcher to ensure the date and numbers were tested separately despite being output on the same line.