Please provide your test method, you are facing some assertion failure and seems your assert in catch block is failing. Would like to see your code.

Your test method needs one of the two following code structures:

public static void testMethod test() {
  Milage_Request__c req = new Milage_Request__c(Name='Test',Miles__c=501);
  try {
    insert req;
  } catch(Exception e) {
    // Awesome, it failed correctly.
  }
}

However, that makes it a bit cumbersome to make sure you actually made it into your try-catch block. An elegant solution would be as follows:

public static void testMethod test() {
  Milage_Request__c req = new Milage_Request__c(Name='Test',Miles__c=501);
  Database.SaveResult sr = Database.insert(req,false);
  System.AssertEquals(sr.isSuccess(),false,'Insert should have failed.');
}

This allows you to assert that the expected behavior occurred. I'd recommend the documentation on the System and Database methods in the Apex Code Developer's Guide.

Hi, thanks for such prompt replies. Here is the code I'm using...

static testMethod void runNegativeTestCases() {

      
       
        
       System.debug('Inserting a record with 501 miles... (negative test case)');
        
       Mileage__c testMiles3 = new Mileage__c( Miles__c = 501, Date__c = System.today() );
        
        try {
            insert testMiles3;
        } catch (DmlException e) {
            //Assert Error Message  
    
            System.assert( e.getMessage().contains('Insert failed. First exception on ' +
                'row 0; first error: FIELD_CUSTOM_VALIDATION_EXCEPTION, ' +
                'Mileage request exceeds daily limit(500): [Miles__c]'), 
                e.getMessage() );
                  
            //Assert field  
    
            System.assertEquals(Mileage__c.Miles__c, e.getDmlFields(0)[0]);
            
            //Assert Status Code  
    
            System.assertEquals('FIELD_CUSTOM_VALIDATION_EXCEPTION' , 
                                 e.getDmlStatusCode(0) );
        } //catch  
    
        
    
    } // runNegativeTestCases()

OK so now I have been trying to get this code working for two days. I have tried numerous ways including a version of the code suggestions posted here. What concerns me most is that apparently, all examples of MileageTracker don't work when it comes to negative case testing. I would love to get to the bottom of this, not just for me but for all other newbies that must get stuck when an example simply doesn't work?

Does anyone know why it doesn't work? It is throwing an exception and then simply failing the test which I thought was the reason for the catch block, so that the exception can be caught and handled gracefully, thus passing the test for a successfullly thrown exception.