.plus(String::class, null)
    assertThat(tags[String::class]).isNull()
    assertThat(tags.toString())
      .isEqualTo("{class kotlin.Int=5, class kotlin.Boolean=true}")
  }

  @Test
  fun removeUntilEmpty() {
    val tags =
      EmptyTags
        .plus(Integer::class, 5 as Integer)
        .plus(Boolean::class, true)
        .plus(String::class, "a")
        .plus(String::class, null)