### Question:
Doubles { public static Mapper<Float, Double> fromFloatToDouble() { return new Mapper<Float, Double>() { @Override public Double map(Float 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 returnsMapperFromFloatToDouble() { assertThat(fromFloatToDouble().map(1234.56F), is(closeTo(1234.56D, 0.001))); }
@Test(expected = NullPointerException.class) public void throwsNullPointerExceptionWhenMapperFromFloatToDoublePassedNull() { fromFloatToDouble().map(null); }