Making assertions about Scala Futures and cats OptionT[Future, T] and EitherT[Future, L, R]

FutureAssertions.scala

import cats.data.{EitherT, OptionT}
import org.scalatest.{Assertion, TestSuite}

import scala.concurrent.Future

trait FutureAssertions {
  self: TestSuite =>

  import org.scalatest.MustMatchers._
  import org.scalatest.concurrent.ScalaFutures._

  implicit class FutureReturns(f: Future[_]) {

    def returns(o: Any): Assertion = whenReady(f)(_ mustBe o)

    def failedWith(e: Exception): Assertion = whenReady(f.failed)(_ mustBe e)

    def failedWith[T <: Throwable](exClass: Class[T]): Assertion = whenReady(f.failed)(_.getClass mustBe exClass)

  }

  implicit class OptionTReturns[T](ot: OptionT[Future, T]) {

    def returnsSome(t: T): Assertion = whenReady(ot.value)(_ mustBe Some(t))

    def returnsNone: Assertion = whenReady(ot.value)(_ mustBe Option.empty[T])

    def failedWith(e: Exception): Assertion = whenReady(ot.value.failed)(_ mustBe e)

  }


  implicit class EitherTReturns[L, R](et: EitherT[Future, L, R]) {

    def returnsRight(value: R): Assertion = whenReady(et.value)(_ mustBe Right(value))

    def returnsLeft(value: L): Assertion = whenReady(et.value)(_ mustBe Left(value))

    def failedWith(e: Exception): Assertion = whenReady(et.value.failed)(_ mustBe e)

  }

}