@Test
public void testPrependHexPrefix() {

    assertThat(Numeric.prependHexPrefix(""), is("0x"));
    assertThat(Numeric.prependHexPrefix("0x0123456789abcdef"), is("0x0123456789abcdef"));
    assertThat(Numeric.prependHexPrefix("0x"), is("0x"));
    assertThat(Numeric.prependHexPrefix("0123456789abcdef"), is("0x0123456789abcdef"));
}