Test-Focused EvaluatorTrace Monad?

Question

Is there infrastructure for writing unit/integration tests for our contracts, without running the full playground? Is there a test-focused EvaluatorTrace monad, for example?

Answer 1

There are now test capabilities in the Plutus.Contract.Test module which uses the Tasty library.

This is explained more fully in the unit tests section of lecture 8 of iteration 1 of the Plutus Pioneer Program.

Some highlights:

checkPredicate :: String -> TracePredicate -> EmulatorTrace () -> TestTree

There are a number of functions for producing a TracePredicate. For example:

-- | Check that the funds in the wallet have changed by the given amount, exluding fees.
walletFundsChange :: Wallet -> Value -> TracePredicate

Which can then be combined into a test function:

tests :: TestTree
tests = checkPredicateOptions
   (defaultCheckOptions & emulatorConfig .~ emCfg)
"token sale trace"
   ( walletFundsChange (Wallet 1) (Ada.lovelaceValueOf   10_000_000  <> assetClassValue token (-60))
.&&. walletFundsChange (Wallet 2) (Ada.lovelaceValueOf (-20_000_000) <> assetClassValue token   20)
.&&. walletFundsChange (Wallet 3) (Ada.lovelaceValueOf (- 5_000_000) <> assetClassValue token    5)
   )
myTrace

Which can then be run like this:

Prelude Spec.Trace> import Test.Tasty
Prelude Test.Tasty Spec.Trace> defaultMain tests
token sale trace: OK (1.22s)

All 1 tests passed (1.22s)

Naturally, these tests can be configured to run as part of "cabal test".

Answer 2

You can use Plutus Playground to test your code and maybe in the near future we will have more options.