PragmaGO.TECH Interview Test - Fee Calculation

Background

This test is designed to evaluate your problem solving approach and your engineering ability. Design your solution in a way that shows your knowledge of OOP concepts, SOLID principles, design patterns, clean and extensible architecture.

Provide a test suite verifying your solution, use any testing framework you feel comfortable with. Use any libraries (or none) you feel add value to your solution. Treat the packaged project as a template; if you feel that your solution can be improved with modifications to it then please go ahead.

The test

The requirement is to build a fee calculator that - given a monetary amount and a term (the contractual duration of the loan, expressed as a number of months) - will produce an appropriate fee for a loan, based on a fee structure and a set of rules described below. A general contract for this functionality is defined in the interface FeeCalculator.

Implement your solution such that it fulfils the requirements.

The fee structure does not follow a formula.
Values in between the breakpoints should be interpolated linearly between the lower bound and upper bound that they fall between.
The number of breakpoints, their values, or storage might change.
The term can be either 12 or 24 (number of months), you can also assume values will always be within this set.
The fee should be rounded up such that fee + loan amount is an exact multiple of 5.
The minimum amount for a loan is 1,000 PLN, and the maximum is 20,000 PLN.
You can assume values will always be within this range but they may be any value up to 2 decimal places.

Example inputs/outputs:

Loan amount	Term	Fee
11,500 PLN	24 months	460 PLN
19,250 PLN	12 months	385 PLN

Installation

A database or any other external dependency is not required for this test.

composer install

Example

<?php

use PragmaGoTech\Interview\Model\LoanProposal;

$calculator = new FeeCalculator();

$application = new LoanProposal(24, 2750);
$fee = $calculator->calculate($application);
// $fee = (float) 115.0

Fee Structure

The fee structure doesn't follow particular algorithm and it is possible that same fee will be applicable for different amounts.

Term 12

1000 PLN: 50 PLN
2000 PLN: 90 PLN
3000 PLN: 90 PLN
4000 PLN: 115 PLN
5000 PLN: 100 PLN
6000 PLN: 120 PLN
7000 PLN: 140 PLN
8000 PLN: 160 PLN
9000 PLN: 180 PLN
10000 PLN: 200 PLN
11000 PLN: 220 PLN
12000 PLN: 240 PLN
13000 PLN: 260 PLN
14000 PLN: 280 PLN
15000 PLN: 300 PLN
16000 PLN: 320 PLN
17000 PLN: 340 PLN
18000 PLN: 360 PLN
19000 PLN: 380 PLN
20000 PLN: 400 PLN

Term 24

1000 PLN: 70 PLN
2000 PLN: 100 PLN
3000 PLN: 120 PLN
4000 PLN: 160 PLN
5000 PLN: 200 PLN
6000 PLN: 240 PLN
7000 PLN: 280 PLN
8000 PLN: 320 PLN
9000 PLN: 360 PLN
10000 PLN: 400 PLN
11000 PLN: 440 PLN
12000 PLN: 480 PLN
13000 PLN: 520 PLN
14000 PLN: 560 PLN
15000 PLN: 600 PLN
16000 PLN: 640 PLN
17000 PLN: 680 PLN
18000 PLN: 720 PLN
19000 PLN: 760 PLN
20000 PLN: 800 PLN

Implementation notes

Never use floating point arithmetic for money calculations.

pawel-slowik / pragmago-recruitment-task