https://medium.com/@riccardoodone/testing-bank-kata-in-purescript-56b1f0a8bb51

Main.purs

main :: Effect Unit
main = do
  testDeposit
  testWithdraw
  testPrintStatementNoTransactions
  testPrintStatementWithTransactions

testDeposit :: Effect Unit
testDeposit = do
  timestamp <- nowDateTime
  let amount = 1
      expected = Identity [ Deposit { amount: amount, timestamp: timestamp } ]
      actual = execStateT (deposit (Identity timestamp) amount) [] 
  assertEqual { actual: actual, expected: expected }

testWithdraw :: Effect Unit
testWithdraw = do
  timestamp <- nowDateTime
  let amount = 1
      expected = Identity [ Withdraw { amount: amount, timestamp: timestamp } ]
      actual = execStateT (withdraw (Identity timestamp) amount) [] 
  assertEqual { actual: actual, expected: expected }

testPrintStatementNoTransactions :: Effect Unit
testPrintStatementNoTransactions = do
  let expected = ""
      actual = execWriter (evalStateT (printStatement \s -> tell s) [])
  assertEqual { actual: actual, expected: expected }

testPrintStatementWithTransactions :: Effect Unit
testPrintStatementWithTransactions = do
  timestamp <- nowDateTime
  let d = Deposit { amount: 500, timestamp: timestamp }
      w = Withdraw { amount: 100, timestamp: timestamp }
      state = [ d, w ]
      expected = "expected string"
      actual = execWriter (evalStateT (printStatement \s -> tell s) state)
  assertEqual { actual: actual, expected: expected }