daml 1.2
module Demo where

template Loan
  with
    owner : Party
  where
    signatory owner

    controller owner can
      Loan_Apply : ContractId Loan
        with
          age : Int
          amount : Decimal
        do
          assertMsg "must be over 18 years of age" $ age > 18
          assertMsg "loan value must be at least 120.00" $ amount >= 120.0

          create this


test_demo = scenario do
  alice <- getParty "alice"

  cid <- submit alice do
    create Loan with owner = alice


  {--
  This example assertion results in the following output

   Scenario execution failed:
   A must-fail commit aborted due to an unexpected failure message
   expected: "must be over 18"
   actual: "loan value must be at least 120.00"
  -}
  submitMustFailMsg alice "must be over 18" do
    exercise cid Loan_Apply with
      age = 19
      amount = 119.00