From https://github.com/marcintustin/http4s-example/blob/master/src/test/scala/com/example/apipractice/HelloWorldTest.scala#L15-L32

HelloWorldTest#L15-L32.scala

  "POST -> /hello/bobo" should "say hello with the greeting specified in the body json" in {
    // org.http4s.Request.withBody returns a task that can be run to generate the request
    val request = org.http4s.Request(Method.POST, uri("/hello/bobo")).withBody(
      """{"greeting": "hola"}""").run


    // run runs the service against the request
    // Note the return type
    val responseTask: scalaz.concurrent.Task[org.http4s.Response] = HelloWorld.service.run(request)


    // the first run gets the org.http4s.Request, which has a body;
    // the body is an org.http4s.EntityBody which is really a scalaz.stream.Process
    // accordingly, to get the value from it, runLast, which itself returns a Task
    // the task needs to be run to obtain an Option of the body as a bytevector
    val response: Option[scodec.bits.ByteVector] = responseTask.run.body.runLast.run


    // Obviously, only use get in test code. decodeUtf8 decodes to an either of a String
    response.get.decodeUtf8.right.get shouldEqual """{"message":"hola, bobo"}"""
  }