DoubleTypeConverter implements TypeConverter<String, Double> { @Override public Double 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 Double.valueOf(value); }  @Override Double convert(final String value);  }
@Test public void whenInputIsLegalValue_ThenShouldReturnDouble() { assertThat(converter.convert("5")).isEqualTo(5D); assertThat(converter.convert("5.0")).isEqualTo(5D); }