Things to notice in the project:

• The UI tests in the AccountFragmentTest don't work due to mocking problems:

    (E/TestRunner: java.lang.IllegalStateException: 		
    Could not initialize plugin: interface 		
    org.mockito.plugins.MockMaker (alternate: null))
  

• The tests of the Repository class could be better tested.

• The extension function or mapper from AcountData to Account takes a bit more than 50ms. I couldn't come up with a better solution, so I decided to go for this one. The way this mapping function works is:

  • From the transactions in an AccountData I map them to a Transaction with a beforeBalance and afterBalance of 0.
  • Then, those transactions inside the list, they are sorted by date (the date in the Transaction model is a LocalDateTime and it can easily compared and thus sorted).
  • And finally, I created a new extension function from a List<Transaction> called map, which given a Transaction from the list, an initial balance, and iterates through every transaction in the list, accumulating the initial balance in the accumulator property, the balanceBefore is assigned the value of the accumulator and the balanceAfter as the sum of the accumulator plus the amount of the transaction. Finally, once the balanceBefore and balanceAfter are initialized with the proper values, the current transaction is copied with the new balanceBefore and balanceAfter values.