So at the end of part 2 we said we don’t like that we have to add the date as part of the public API. Which makes sense for a public bank terminal, we do a deposit or withdrawal now. So we’ll want to remove on from deposit and withdrawal. But where do the dates come from now? Let’s introduce a Clock module: Let’s see if we can rewrite our test to adapt to this new API »
In part 1 we’ve set everything up, let’s implement the kata now. If we check the readme we can see a simple acceptance test, let’s start with that. We create a file test/account_test.ml: open! Base open! Stdio let%expect_test "Printing the statements should contain all transactions" = Lib.Account.create () |> Lib.Account.deposit ~amount:1000.0 ~on:"10/01/2012" |> Lib.Account.deposit ~amount:2000.0 ~on:"13/01/2012" |> Lib.Account.withdrawal ~amount:500.0 ~on:"14/01/2012" |> Lib.Account.print; [%expect{| date || amount || balance 14/01/2012 || -500. »
The goal of this small series of blogs is to implement the Bank kata in OCaml, doing it test and type driven and try to have a clean design. We’ll try to implement the kata with outside-in tests. My personal goal is to learn some OCaml along the way. I won’t be going into every detail of OCaml, but if you have some experience with an ML language, you should be able to follow along. »