BigIntegerTypeConverter implements TypeConverter<String, BigInteger> { @Override public BigInteger convert(final String value) { Utils.checkArgument(value != null, "Value to convert must not be null"); Utils.checkArgument(!value.isEmpty(), "Value to convert must not be empty"); return new BigInteger(value); }  @Override BigInteger convert(final String value);  }
@Test public void whenInputIsLegalValue_ThenShouldReturnBigInteger() { assertThat(converter.convert("5")).isNotNull(); assertThat(converter.convert("5").intValue()).isEqualTo(5); }