### Question:
FacetPrefixedValueConverter implements FacetValueConverter { @Override public Object convert(String value, XSettings xsettings) { Preconditions.checkNotNull(value); return fieldValuePrefixAdder.extractFieldValue(value); }  @Override Object convert(String value, XSettings xsettings); @Override boolean handles(XSettings xsettings); @Autowired void setFieldValuePrefixAdder(FieldValuePrefixAdder fieldValuePrefixAdder);  }### Answer:
@Test(expected = NullPointerException.class) public void convert_NullValue() { converter.convert(null, mock(XSettings.class)); }
@Test public void convert() { String value = "PREFIX_VALUE"; when(fieldValuePrefixAdder.extractFieldValue(value)).thenReturn("VALUE"); assertEquals("VALUE", converter.convert(value, null)); }