set("a", "a1", "a2")
    val iterator = cache.snapshots()
    assertFailsWith<IllegalStateException> {
      iterator.remove()
    }
  }

  @Test
  fun iteratorRemoveOncePerCallToNext() {
    set("a", "a1", "a2")
    val iterator = cache.snapshots()
    iterator.next().use {
      iterator.remove()
    }
    assertFailsWith<IllegalStateException> {
      iterator.remove()

    val i = cache.urls()
    assertThat(i.hasNext()).isTrue()
    assertFailsWith<IllegalStateException> {
      i.remove()
    }
  }

  @Test
  fun iteratorRemoveOncePerCallToNext() {
    // Put a response in the cache.
    server.enqueue(
      MockResponse
        .Builder()
        .body("a")
        .build(),
    )
    val url = server.url("/a")