@Test
  public void testSettingNormalizationWhenNormalizationAlreadySet() {
    assertIllegalNormalizations(NFC, NFC);
    assertIllegalNormalizations(NFC, NFD);
    assertIllegalNormalizations(CASE_FOLD_ASCII, CASE_FOLD_ASCII);
    assertIllegalNormalizations(CASE_FOLD_ASCII, CASE_FOLD_UNICODE);
  }
Tests for {@link Configuration}, {@link Configuration.Builder} and file systems created from
them.

@author Colin Decker
jimfs/src/test/java/com/google/common/jimfs/ConfigurationTest.java