Scala single-file drop-in testing framework

SelfTest.scala

import scala.concurrent.Future
import scala.scalajs.js
import scala.util.Success
import scala.util.Failure

object SelfTest {
  def GREEN_CIRCLE: String = "\uD83D\uDFE2"
  def RED_CIRCLE: String = "\uD83D\uDD34"

  def runTests(): Unit = {
    runTestSync("test1", test1)
    runTestSync("test2", test2)
    runTestAsync("test3", test3)
  }

  def test1(): Unit = {
    var expected = "1"
    var actual = Integer.toString(1);
    assertEquals(expected, actual)
  }

  def test2(): Unit = {
    val expected = "2"
    val actual = 1.toString()
    assertEquals(expected, actual)
  }

  def test3(): Future[Unit] = {
    val future = OdrsClient.fetchRatings()
    future.map(s => assertEquals(7412, s.size))
  }

  private def runTestSync(testName: String, testMethod: () => Unit): Unit = {
    val errorMsg = 
      try {
        testMethod()
        Option.empty
      } catch {
        case e: Exception => 
          Some(e.toString())
      }
    val toPrint = if (errorMsg.isEmpty) then GREEN_CIRCLE else s"$RED_CIRCLE. ${errorMsg.get}"
    println(s"Test $testName: ${toPrint}")
  }

  private def runTestAsync(testName: String, testMethod: () => Future[Unit]): Unit = {
    val res = testMethod.apply()
    res.onComplete {
      case Success(s) => {
        println(s"Test $testName: $GREEN_CIRCLE")
      }
      case Failure(ex) => {
        println(s"Test $testName: $RED_CIRCLE. ${ex.toString()}")
      }
    }
  }

  private def assertEquals(expected: Any, actual: Any): Unit = {
    if (!expected.equals(actual)) {
      throw new RuntimeException("Failed: expected " + expected + ", got " + actual)
    }
  }

}