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Money Problem

This kata comes from Saleem Siddiqui 's book

img/Learning-Test-Driven-Development.jpg

What's the problem ?

We have to build a spreadsheet to manage money in more than one currency : perhaps to manage a stock portfolio ?

Stock Stock exchange Shares Share Price Total
IBM NASDAQ 100 124 USD 12400 USD
BMW DAX 400 75 EUR 30000 EUR
Samsung KSE 300 68000 KRW 20400000 KRW

To build it, we'd need to do simple arithmetic operations on numbers :

5 USD x 2 = 10 USD
4002 KRW / 4 = 1000.5 KRW

// convert
5 USD + 10 EUR = 17 USD
1 USD + 1100 KRW = 2200 KRW
  • We can use this table to determine exchange rates :
From To Rate
EUR USD 1.2
USD EUR 0.82
USD KRW 1100
KRW EUR 0.0009
EUR KRW 1344
KRW EUR 0.00073

List of Features to implement

We have already started the implementation by using TDD. We have discovered examples that helped us drive our implementation.

Money Calculator :
✅ 10 EUR x 2 = 20 EUR
✅ 4002 KRW / 4 = 1000.5 KRW
✅ 5 USD + 10 USD = 15 USD

Bank implementation :
✅ Determine exchange rate based on the currencies involved (from -> to)
✅ Improve the implementation of exchange rates
✅ Allow exchange rates to be modified

Constraints

You will have to develop using the main constraints:

  • Test-Driven Development
  • Pair Programming

Xtrem Iteration

We will work in small iterations

Xtrem iteration

  • Share the constraint
  • Implement it in your code
  • Debriefing
    • How did you apply it?
    • What did you learn?
    • How could it be useful in your current code base?
    • Our solution
      • Keep your code or switch to our solution branch to move on

Iterations

In this workshop, we will make those iterations in this order:

  1. Let's Mutate Some Code
  2. Implement Portfolio
  3. Fight Primitive Obsession
  4. No For Loops
  5. Use Only Immutable Types
  6. Avoid Exceptions
  7. Use an existing monad
  8. Property-Based Testing to challenge our Domain Model
  9. Shared understanding on the Bank with Example Mapping
  10. Redesign the Bank
  11. Add an Acceptance Test
  12. Functional Core, Imperative Shell

Solution

We have created 1 branch per iteration solution

Branches

Each branch contains:

  • a possible solution for the given constraint in java, c# and scala
  • a step-by-step guide to reproduce how we came from previous state to the state in the branch
    • 1 guide per language in <language>/docs/<#iteration>.<constraint>.md