How can i write unit test for ddmmYYYY validation with use java/spring?

Question

    Accepting DateFormat : 01042021

1. List item

   Incorrect DateFormat : 9901042021 or 0104202199 etc.
   

   My date validation code blocks:

       @Value("${sms.date.format:ddMMyyyy}")
       private String DATE_FORMAT;
   
       public void validateDates(ReportRequest request){
   
           DateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT);
   
           if(StringUtils.isNotBlank(request.getStartDate())){
               try{
                   dateFormat.parse(request.getStartDate());
               }catch (Exception e){
                   throw new InvalidInputException("Invalid start date format, must be as : " +DATE_FORMAT);
               }
           } else {
               throw new InvalidInputException("Contract start date is empty");
   
           }
   
           if(StringUtils.isNotBlank(request.getEndDate())){
               try{
                   dateFormat.parse(request.getEndDate());
               }catch (Exception e){
                   throw new InvalidInputException("Invalid end date format, must be as : " +DATE_FORMAT);
               }
           } else {
               throw new InvalidInputException("Contract end date is empty");
   
           }
       }
   

   My Unit Test: Getting error on first line because dateformat is null how can i fix it?

   @Value("${sms.date.format:ddMMyyyy}")
   private String DATE_FORMAT;
   
   public void testValidateDates() {
   
   
           DateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT);
           ReportRequest reportRequest = new ReportRequest();
           ReportRequest.setStartDate("0104202199");
           ReportRequestValidator reportRequestValidator = new ReportRequestValidator();
           ReportRequestValidator.validateDates(reportRequest);
           assertEquals("Invalid start date format, must be as : ","0104202199");
   
       }
   

   How should I use the assert function, what should the condition be?

Answer 1

The problem is that DATE_FORMAT is not injected into your test class, so you get a NullPointerException.

Two way to solve it

1. use @SpringBootTest. Check this: https://www.baeldung.com/spring-tests-override-properties

2. a more clean way: without any Spring annotation. This makes the test code much simpler. Just refactor your code:

// in your production code:
public class ReportRequestValidator {

  private String DATE_FORMAT;

  // package-private constructor for test 
  ReportRequestValidator (@Value("${sms.date.format:ddMMyyyy}") String dateFormat) {
     DATE_FORMAT = dateFormat;
  }

  // business logic...
 
}


// in your test code

@Rule
public ExpectedException expectedEx;

@Before
public void init() {
  expectedEx = ExpectedException.none();
}

@Test
public void testValidateDates() {
    String DATE_FORMAT = "PROVIDE_DATE_FORMAT_STRING_BY_YOURSELF";
    ReportRequest reportRequest = new ReportRequest();
    ReportRequest.setStartDate("0104202199");
    ReportRequestValidator reportRequestValidator = new ReportRequestValidator(DATE_FORMAT);    // inject DATE_FORMAT into validator

    ReportRequestValidator.validateDates(reportRequest);

    expectedEx.expect(InvalidInputException.class);
    expectedEx.expectMessage("Invalid start date format, must be as : 0104202199");
}