### Question:
Doubles { public static Mapper<Long, Double> fromLongToDouble() { return new Mapper<Long, Double>() { @Override public Double map(Long input) { return input.doubleValue(); } }; }  static Mapper<String, Double> fromStringToDouble(); static Mapper<Integer, Double> fromIntegerToDouble(); static Mapper<Long, Double> fromLongToDouble(); static Mapper<BigInteger, Double> fromBigIntegerToDouble(); static Mapper<Float, Double> fromFloatToDouble(); static Mapper<BigDecimal, Double> fromBigDecimalToDouble();  }### Answer:
@Test public void returnsMapperFromLongToDouble() { assertThat(fromLongToDouble().map(1234L), is(1234D)); }
@Test(expected = NullPointerException.class) public void throwsNullPointerExceptionWhenMapperFromLongToDoublePassedNull() { fromLongToDouble().map(null); }