expected: Thread[test,5,main]
but was : Thread[main @coroutine#1,5,main]

Thread.currentThread().getId()

expected: 21
but was : 1

runBlocking

@Test fun isolateFailing() = runBlocking(TestCoroutineDispatcher()) {
    var outerThread: Thread? = nullThread.currentThread()
    val singleThreadedContext = newSingleThreadContext("test")
    var innerThread: Thread? = null
    val function = suspend {
      outerThread = Thread.currentThread()
      innerThread = withContext(this@runBlocking.coroutineContext) {
        Thread.currentThread()
      }
    }

    val job = launch {
      withContext(singleThreadedContext) {
        function()
      }
    }

    job.join()
    assertThat(outerThread).isNotEqualTo(innerThread)
  }

expected not to be: Thread[test,5,main]

* By default, [TestCoroutineDispatcher] is immediate. That means any tasks scheduled to be run without delay are
 * immediately executed. If they were scheduled with a delay, the virtual clock-time must be advanced via one of the
 * methods on [DelayController].