Hi all,

I hope someone can help me here as my knowledge in APEX is rudimentary but willing to learn very much.
I was wondering how would the test class to this APEX code of a custom Case controller look like:
 

public class case_controller {

    public case_controller(ApexPages.StandardController controller) {

    }


public String case_FirstName{get;set;}
public String case_LastName{get;set;}
public String case_Email{get;set;}

public String casetype_Esp{get;set;}
public String casetype_Cat{get;set;}
public String casetype_En{get;set;}

public String userLanguage{get;set;}
public Boolean showCaptchaField {get;set;}

// Variables para control de errores
public Boolean show_error{get;set;}
public Boolean error_dni{get;set;}
public Boolean error_no_existe{get;set;}
public Boolean error_dni_case{get;set;}


public String phone_prefix{get;set;}
public Account student{get;set;}

public Case incident{get;set;}

public String array_values{get;set;} 

public String areaSelected{get;set;}
public String areaSelectedEsp{get;set;}
public String areaSelectedEn{get;set;}
public String areaSelectedCat{get;set;}

Public Product2 postgraduatecourseCaso{get;set;}
public String postgraduatecourseSelected{get;set;}
public String postgraduatecourseSelectedText{get;set;}

public List<SelectOption> casetypeOptionsEsp{get;set;} 
public List<SelectOption> casetypeOptionsEn{get;set;} 
public List<SelectOption> casetypeOptionsCat{get;set;} 

public List<SelectOption> motivocasoOptionsEsp{get;set;} 
public List<SelectOption> motivocasoOptionsEn{get;set;} 
public List<SelectOption> motivocasoOptionsCat{get;set;} 

public String IdentificationType_Esp{get;set;} 
public String IdentificationType_En{get;set;} 
public String IdentificationType_Cat{get;set;} 

public List<SelectOption> identificationOptionsEsp{get;set;} 
public List<SelectOption> identificationOptionsEn{get;set;} 
public List<SelectOption> identificationOptionsCat{get;set;} 

public List<SelectOption> areaOptionsEsp{get;set;} 
public List<SelectOption> areaOptionsEn{get;set;} 
public List<SelectOption> areaOptionsCat{get;set;} 


public List<SelectOption> postgraduatecourseOptions{
    get{
        String areaSelected = 'none';
        if(userLanguage == 'Es') areaSelected = areaSelectedEsp;
            else if(userLanguage == 'En') areaSelected = areaSelectedEn;
            else if(userLanguage == 'Cat') areaSelected = areaSelectedCat;

        postgraduatecourseOptions = FormUtils.getpostgraduatecourseOpt(areaSelected, userLanguage); 
        return postgraduatecourseOptions;
        
    }set;
}



private void resetErrors(){
    show_error = false;
    error_dni = false;
    error_no_existe = false;
    error_dni_case = false;
}

public case_controller(){
    incident = new Case();
    resetErrors();
    getListOptions();
    
// El captcha es mostrado sólo cuando la página está en la Web, no si la página se usa para registrar casos en la misma aplicación
  showCaptchaField = !UserUtils.isCurrentUserProfileSecretariaTecnica();
}

// Registrar un caso
public pageReference case_submit(){
   Savepoint sp = Database.setSavepoint();
    String language;
    try{    

        if (userLanguage =='En'){
            language = 'English';
            incident.preferred_language__c = 'English';
            incident.Identification_number_type__c = IdentificationType_En;
            //incident.DNI__c = IdentificationNumber_En;
            incident.Type = casetype_En;
            //incident.Reason = motivocaso_En;
        }
        else if (userLanguage =='Cat'){
            language = 'Catalan';
            incident.preferred_language__c = 'Catalan';
            incident.Identification_number_type__c = IdentificationType_Cat;
            //incident.DNI__c = IdentificationNumber_Cat;
            incident.Type = casetype_Cat;
            //incident.Reason = motivocaso_Cat;
        }
        else{
            language = 'Spanish';
            incident.preferred_language__c = 'Spanish';
            incident.Identification_number_type__c = IdentificationType_Esp;
            //incident.DNI__c = IdentificationNumber_Esp;
            incident.Type = casetype_Esp;
            //incident.Reason = motivocaso_Esp;
        } 

        System.debug('*************** case forms ///// incident '+ incident);
        

        //Preparing the data to create a case

        insert(incident);
    }catch(Exception e){
        system.debug('Exception :' + e);
    }  

    pageReference pageRef = new PageReference('/apex/case_answer_form');
    pageRef.getParameters().put('type','case_form');
    pageRef.getParameters().put('id',student.id);
    pageRef.getParameters().put('lng', userLanguage);
    return pageRef;
}
/**TODO: sacarlo a clase Utils
private Id getAccountIdFromDNI(String dni){
    Account acc = new Account();
    list<Account> accountList = [Select id, FirstName, LastName, DNI__c From Account Where DNI__c = : dni];
    if (accountList != null && accountList.size()>0){
        acc = accountList[0];
    }
    return acc.Id;

}*/

This code is about inserting a case with the values given in the VF form for the fields Postgraduate Course, FirstName, LastName, Email, Type of case, Reason.
I would appreciate any orientation