### Question:
BigIntegers { public static Mapper<String, BigInteger> fromStringToBigInteger() { return new Mapper<String, BigInteger>() { @Override public BigInteger map(String input) { return new BigInteger(input); } }; }  static Mapper<String, BigInteger> fromStringToBigInteger(); static Mapper<Integer, BigInteger> fromIntegerToBigInteger(); static Mapper<Long, BigInteger> fromLongToBigInteger(); static Mapper<Float, BigInteger> fromFloatToBigInteger(); static Mapper<Double, BigInteger> fromDoubleToBigInteger(); static Mapper<BigDecimal, BigInteger> fromBigDecimalToBigInteger();  }### Answer:
@Test public void returnsMapperFromStringToBigInteger() { assertThat(fromStringToBigInteger().map("12345678"), is(new BigInteger("12345678"))); }
@Test(expected = NullPointerException.class) public void throwsNullPointerExceptionWhenMapperFromStringToBigIntegerPassedNull() { fromStringToBigInteger().map(null); }