@SuppressWarnings("nullness") // test of a bogus call
  public void testNullMap() {
    assertThrows(NullPointerException.class, () -> ArrayBasedEscaperMap.create(null));
  }

  public void testEmptyMap() {
    Map<Character, String> map = ImmutableMap.of();
    ArrayBasedEscaperMap fem = ArrayBasedEscaperMap.create(map);
    // Non-null array of zero length.
    assertThat(fem.getReplacementArray()).isEmpty();
  }