typelevel / munit-cats-effect

Integration library for MUnit & cats-effect

Version Matrix


Integration library for MUnit and cats-effect.


Cats Effect 2 integration is provided via:

libraryDependencies += "org.typelevel" %%% "munit-cats-effect-2" % "0.11.0" % "test"

Cats Effect 3 integration is provided via:

libraryDependencies += "org.typelevel" %%% "munit-cats-effect-3" % "0.11.0" % "test"

Builds are available for Scala 2.12, 2.13, and 3 for both the JVM and Scala.js.

Getting Started

The munit.CatsEffectSuite trait provides the ability to write tests that return IO and SyncIO values without needing to call any unsafe methods (e.g. unsafeRunSync()).

import cats.effect.{IO, SyncIO}
import munit.CatsEffectSuite

class ExampleSuite extends CatsEffectSuite {

  test("tests can return IO[Unit] with assertions expressed via a map") {
    IO(42).map(it => assertEquals(it, 42))

  test("alternatively, asertions can be written via assertIO") {
    assertIO(IO(42), 42)

  test("or via assertEquals syntax") {

  test("or via plain assert syntax on IO[Boolean]") {

  test("SyncIO works too") {

  import cats.effect.std.Dispatcher

  val dispatcher = ResourceFixture(Dispatcher[IO])

  dispatcher.test("resources can be lifted to munit fixtures") { dsp =>

There are more assertion functions like interceptIO and interceptMessageIO as well as syntax versions intercept and interceptMessage. See the CatsEffectAssertions trait for full details.