Cardano Smart Contract Testing

Scalus provides comprehensive testing tools for Cardano smart contracts — unit testing, debugging, and local execution environments.

Testing Tools Overview

Tool	Purpose	Best For
Unit Testing	Property-based tests with ScalaCheck	Validator logic verification
Debugging	IDE debugging, logging, error traces	Finding and fixing bugs
Emulator	In-memory Cardano node	Fast iteration, CI/CD
Local Devnet	Docker-based real Cardano node	Integration tests, pre-deployment

Unit Testing with ScalaCheck

Write property-based tests using ScalaCheck to verify validator logic:


class MyValidatorTest extends AnyFunSuite with ScalusTest {
  test("validator accepts valid signature") {
    val txInfo = random[TxInfo]
    val signer = random[PubKeyHash]
    // Test your validator logic
  }
}

See Unit Testing for complete guide.

Debugging

Debug validators as regular Scala code — use IDE breakpoints, step through execution, and inspect variables:


@Compile
object MyValidator extends Validator:
  inline override def spend(...): Unit = {
    log("Starting validation")
    val owner = datum.getOrFail("No datum").to[PubKeyHash]
    // Set breakpoint here, inspect variables
    require(tx.signatories.contains(owner), "Not signed")
  }

See Debugging for IDE setup and logging.

Local Execution Environments

Emulator — Fast In-Memory Testing

The Emulator validates transactions and executes Plutus scripts instantly — no Docker required:


val emulator = Emulator.withAddresses(Seq(Alice.address, Bob.address))
 
val tx = TxBuilder(testEnv)
  .payTo(Bob.address, Value.ada(10))
  .complete(emulator, Alice.address)
  .await()
  .sign(Alice.signer)
  .transaction
 
emulator.submit(tx).await() // Instant validation + script execution

Local Devnet — Real Cardano Node

Local Devnet runs a real Cardano node (Yaci DevKit) in Docker:


class MyTest extends AnyFunSuite with YaciDevKit {
  test("submit transaction to local devnet") {
    val ctx = createTestContext()
    val tx = TxBuilder(ctx.cardanoInfo)
      .payTo(recipient, Value.ada(10))
      .complete(ctx.provider, ctx.address)
      .await(30.seconds)
      .sign(ctx.signer)
      .transaction
 
    ctx.submitTx(tx) // Real Cardano node validation
  }
}

Recommended Workflow

Test pyramid: Tests → Emulator → Local Devnet → Testnet → Mainnet

Development: Write code → Run tests → Emulator → Fast feedback → Debug with IDE

Pre-deployment: All tests pass → Local Devnet → Deploy with confidence