We did a minor modification to our code in the If/Else statement in our class, now I am trying to reach 100% test coverage. As you can see in my test class below, i inserted a new contact as coTeacher and a new class as newCLass and populated the fields with the new contact Ids in newClass, but my test coverage is still at 84%, I am getting the following error:
System.DmlException: Insert failed. First exception on row 0; first error: FIELD_FILTER_VALIDATION_EXCEPTION, This person is not a qualified instructor. Please select a qualified instructor.: [Instructor__c]
What am I missing? any help would be much appreciated.

public class ClassSelectorController {
  public List<Class__c> classes { get; set; }
  String dayFormat = 'MM/DD';
  public Id classId { get; set; }
  public String userEmail { get; set; }
  public String userProfileId;
  public Profile gwCommunityProfile;
  public Id classType { get; set; }

  public ClassSelectorController() {
    userEmail = UserInfo.getUserEmail();
    userProfileId = UserInfo.getProfileId();
    gwCommunityProfile = [
      SELECT Id, Name
      FROM Profile
      WHERE Name = 'GW Community User'
      LIMIT 1
    ];
    System.debug(gwCommunityProfile);
    System.debug(gwCommunityProfile.Id);
    System.debug(userProfileId);
    getClasses();
  }
  public void getClasses() {
    // Limit visibility to GW community user
    if (userProfileId != gwCommunityProfile.Id) {
      classes = [
        SELECT
          id,
          name,
          class_nights__c,
          start_date__c,
          end_date__c,
          status__c,
          class__c,
          instructor__r.email,
          RecordTypeId
        FROM class__c
        WHERE status__c = 'Active'
      ];
      System.debug(classes);
    } else {
      classes = [
        SELECT
          id,
          name,
          class_nights__c,
          start_date__c,
          end_date__c,
          status__c,
          class__c,
          instructor__r.email,
          RecordTypeId
        FROM class__c
        WHERE
          status__c = 'Active'
          AND (instructor__r.Email = :userEmail
          OR Co_Teacher__r.Email = :userEmail
          OR Teachers_Assistant__r.Email = :userEmail)
      ];
      System.debug(classes);
    }
  }

  public Pagereference newPage() {
    Id cohortRecordTypeId = Schema.SObjectType.class__c.getRecordTypeInfosByName()
      .get('Cohort')
      .getRecordTypeId();
    String url = '/apex/BWRoster?id=' + classId;
    if (classType == cohortRecordTypeId) {
      url += '&type=Cohort';
    }

    return new PageReference(url);
  }
}

Test Coverage

@isTest
public class ClassSelectorTest {
    
    static testMethod void testGetClassesGWProfile() {    
        
        Profile gwCommunityProfile = [SELECT Id FROM Profile WHERE Name = 'GW Community User' LIMIT 1];
        Contact teacher = new Contact(FirstName = 'Teacher', LastName = 'Teaher', Email = 'teacher@teacher.com');
        insert teacher;

        Contact coTeacher = new Contact(FirstName = 'co-teacher', LastName = 'co-teacher', Email = 'co-teacher@co-teacher.com');
        insert coTeacher;

         // Contact assistant = new Contact(FirstName = 'assistant', LastName = 'asistant', Email = 'assistant@assistant.com');
         // insert assistant;


        // User gwCommunityUser = new User(FirstName='Teacher', LastName='Teacher', ContactId = teacher.Id, Email='teacher@teacher.com', ProfileId= gwCommunityProfile.Id);
        // insert gwCommunityUser;
    
        // System.debug(gwCommunityUser);

        class__c newClass = new class__c(name = 'Test Class', Instructor__c = teacher.Id, Co_Teacher__c = coTeacher.Id,
        class_nights__c = 'Monday / Wednesday', start_date__c = date.today() - 10, end_date__c = date.today() + 45);
        insert newClass;

        

        ClassSelectorController pc = new ClassSelectorController();
        pc.userEmail = 'teacher@teacher.com';
        
        pc.userProfileId = gwCommunityProfile.Id;
        
        pc.getClasses();
        
        System.assertEquals(1, pc.classes.size());
    }
 @isTest
  public static void testURLIsCohort(){
    String CohortRecordTypeId = Schema.SObjectType.class__c.getRecordTypeInfosByName().get('Cohort').getRecordTypeId();
    class__c newClass = new class__c(name = 'Test Class', RecordTypeId = CohortRecordTypeId, class_nights__c = 'Monday / Wednesday', start_date__c = date.today() - 10, end_date__c = date.today() + 45);
    insert newClass;
    
    CLassSelectorController gwClass = new ClassSelectorController();
    gwClass.classId = newClass.Id;
    gwClass.classType = newClass.RecordTypeId;
    PageReference rosterPage = gwClass.newPage();
    System.assertEquals('/apex/BWRoster?id='+newClass.Id + '&type=Cohort',rosterPage.getUrl());
        
        
    }
}