@Test
  public void randKeyId_repeatedCallsShouldOutputDifferentValues() {
    assertThat(
            (int) IntStream.range(0, 4).map(unused -> Util.randKeyId()).boxed().distinct().count())
        .isAtLeast(2);
  }
Tests for Tink internal Util class.
java_src/src/test/java/com/google/crypto/tink/internal/UtilTest.java