With Manual TestContext Creation

TestContext

cats.effect.kernel.testkit.TestContext is from cats-effect-kernel-testkit and it is

A scala.concurrent.ExecutionContext implementation that can simulate async boundaries and time passage

extras-hedgehog-ce3 uses it and if you need to manually create it you can do so if you do not use withIO or runIO.

implicit val ticker: Ticker = Ticker.withNewTestContext()

Ticker is a value class for TestContext so you can also do

import cats.effect.kernel.testkit.TestContext
import extras.hedgehog.ce3.Ticker // You don't need to import it if you're using CatsEffectRunner

implicit val ticker: Ticker = Ticker(TestContext())

completeThen

Use CatsEffectRunner and completeThen instead of unsafeRunSync().

import cats.effect._

import extras.hedgehog.ce3.CatsEffectRunner

import hedgehog._
import hedgehog.runner._

object SomeSpec extends Properties with CatsEffectRunner {
  
  override def tests: List[Test] = List(
    property("test with CatsEffectRunner and completeThen", testCatsEffectRunnerWithCompleteThen)
  )
  
  def testCatsEffectRunnerWithCompleteThen: Property = for {
    n <- Gen.int(Range.linear(Int.MinValue, Int.MaxValue)).log("n")
  } yield {
    implicit val ticker: Ticker = Ticker.withNewTestContext()

    val expected = n
    val actual = IO(n)

    actual.completeThen { actual =>
      actual ==== expected
    }
  }
}

errorThen

If you want to test with IO which may result in some Exception thrown, you can use errorThen instead of unsafeRunSync() and Try.

import cats.effect._

import extras.hedgehog.ce3.CatsEffectRunner

import hedgehog._
import hedgehog.runner._

object SomeSpec extends Properties with CatsEffectRunner {

  override def tests: List[Test] = List(
    property("test with CatsEffectRunner and errorThen", testCatsEffectRunnerWithErrorThen)
  )

  def testCatsEffectRunnerWithErrorThen: Property = for {
    message <- Gen.string(Gen.alphaNum, Range.linear(1, 10)).log("message")
    error <- Gen
      .element1(
        TestError.someTestError(s"Don't worry it's only a test error. $message"),
        TestError.anotherTestError(s"Don't worry it's only a test error. $message")
      )
      .log("error")
  } yield {
    implicit val ticker: Ticker = Ticker.withNewTestContext()

    val expected = error
    val actual = IO.raiseError[Int](error)

    actual.errorThen { actual =>
      actual ==== expected
    }
  }

  sealed abstract class TestError(val message: String) extends RuntimeException(message)

  object TestError {
    final case class SomeTestError(override val message: String) extends TestError(message)
    final case class AnotherTestError(override val message: String) extends TestError(message)

    def anotherTestError(message: String): TestError = AnotherTestError(message)
    def someTestError(message: String): TestError = SomeTestError(message)

  }
}