bank-kata-haskell-print-8.hs

testPrintStatement :: StateT [Transaction] (Writer String) ()
testPrintStatement = innerPrintStatement (\statement -> tell statement)

it "prints a statement" $ do
  -- evalStateT works just like evalState, except it will return us a `Writer String ()` instead of just `()`
  -- we can then use execWriter to get the String from Writer String ()
  execWriter (evalStateT testPrintStatement [Deposit 100, Withdrawal 50]) `shouldBe` "Deposited 100\nWithdrew 50"