### Question:
FieldNoOpFilter implements FieldFilter { @Override public List<Field> filter(DescribeSObjectResult dsr) { if (dsr == null) return null; return Lists.newArrayList(dsr.getFields()); }  @Override List<Field> filter(DescribeSObjectResult dsr);  }### Answer:
@Test public void testFilterWithNullValue() { assertNull(new FieldNoOpFilter().filter(null), "A no op filter of a null value should be null"); }
@Test public void testFilterWithNonNullValue() { DescribeSObjectResult dsr = new DescribeSObjectResult(); dsr.setName("Object_Name__c"); Field idField = new Field(); idField.setName("Id"); idField.setType(FieldType.id); Field nameField = new Field(); nameField.setName("Name"); nameField.setType(FieldType.string); dsr.setFields(new Field[] { idField, nameField }); List<Field> filteredFields = new FieldNoOpFilter().filter(dsr); assertNotNull(filteredFields, "A no op filter of a non-null value should be non-null"); assertEquals(filteredFields.size(), 2, "Unexpected number of Fields after no op filter"); assertEquals(filteredFields.get(0).getName(), "Id", "Unexpected Field order after no op filter"); }