val snapshot = cache["k1"]
    assertThat(snapshot).isNull()
  }

  @Test
  fun validateKey() {
    var key = ""
    assertFailsWith<IllegalArgumentException> {
      key = "has_space "
      cache.edit(key)
    }.also { expected ->
      assertThat(expected.message).isEqualTo("keys must match regex [a-z0-9_-]{1,120}: \"$key\"")
    }
    assertFailsWith<IllegalArgumentException> {

	// This is an exact count if s is ASCII, otherwise it is an approximation.
	n := 0
	wasSpace := 1
	// setBits is used to track which bits are set in the bytes of s.
	setBits := uint8(0)
	for i := 0; i < len(s); i++ {
		r := s[i]
		setBits |= r
		isSpace := int(asciiSpace[r])
		n += wasSpace & ^isSpace
		wasSpace = isSpace
	}

	if setBits >= utf8.RuneSelf {
		// Some runes in the input slice are not ASCII.