Usually this problem occurs when the written test is not run. After writing the test, run it at least 1 time and try.

# SOLUTION

1.  In the Developer Console, click **File** | **New** | **Apex Class**, and enter **VerifyDate** for the class name, and then click **OK**.
    
2.  Replace the default class body with the following.

public class VerifyDate {
        
        //method to handle potential checks against two dates
        public static Date CheckDates(Date date1, Date date2) {
            //if date2 is within the next 30 days of date1, use date2.  Otherwise use the end of the month
            if(DateWithin30Days(date1,date2)) {
                return date2;
            } else {
                return SetEndOfMonthDate(date1);
            }
        }
        
        //method to check if date2 is within the next 30 days of date1
        private static Boolean DateWithin30Days(Date date1, Date date2) {
            //check for date2 being in the past
                if( date2 < date1) { return false; }
            
                //check that date2 is within (>=) 30 days of date1
                Date date30Days = date1.addDays(30); //create a date 30 days away from date1
            if( date2 >= date30Days ) { return false; }
            else { return true; }
        }
    
        //method to return the end of the month of a given date
        private static Date SetEndOfMonthDate(Date date1) {
            Integer totalDays = Date.daysInMonth(date1.year(), date1.month());
            Date lastDay = Date.newInstance(date1.year(), date1.month(), totalDays);
            return lastDay;
        }
    
    }

    
3.  Press Ctrl+S to save your class.
    
4.  In the Developer Console, click **File** | **New** | **Apex Class**, and enter **TestVerifyDate** for the class name, and then click **OK**.
    
5.  Replace the default class body with the following.
    
  

@isTest
    private class TestVerifyDate {
    
        //testing that if date2 is within 30 days of date1, should return date 2
        @isTest static void testDate2within30daysofDate1() {
            Date date1 = date.newInstance(2018, 03, 20);
            Date date2 = date.newInstance(2018, 04, 11);
            Date resultDate = VerifyDate.CheckDates(date1,date2);
            Date testDate = Date.newInstance(2018, 04, 11);
            System.assertEquals(testDate,resultDate);
        }
        
        //testing that date2 is before date1. Should return "false"
        @isTest static void testDate2beforeDate1() {
            Date date1 = date.newInstance(2018, 03, 20);
            Date date2 = date.newInstance(2018, 02, 11);
            Date resultDate = VerifyDate.CheckDates(date1,date2);
            Date testDate = Date.newInstance(2018, 02, 11);
            System.assertNotEquals(testDate, resultDate);
        }
        
        //Test date2 is outside 30 days of date1. Should return end of month.
        @isTest static void testDate2outside30daysofDate1() {
            Date date1 = date.newInstance(2018, 03, 20);
            Date date2 = date.newInstance(2018, 04, 25);
            Date resultDate = VerifyDate.CheckDates(date1,date2);
            Date testDate = Date.newInstance(2018, 03, 31);
            System.assertEquals(testDate,resultDate);
        }  
    }

    
6.  Press Ctrl+S to save your class.
    
7.  In the Developer Console, click **Test** | **New Run**.
    
8.  Under **Test Classes**, click **TestVerifyDate**.
    
9.  To add all the test methods in the **TestVerifyDate** class to the test run, click **Add Selected**.
    
10. Click **Run**.
    
11. In the Tests tab, you see the status of your tests as they’re running. Expand the test run, and expand again until you see the list of individual tests that were run. They all have green checkmarks.