Please help me out with the test class for the below class

public class DonorDetailsController
{
        public List<CommitmentDetails> commitmentDetailsList {get;set;}
        public List<PaymentDetails> paymentDetailsList {get;set;}
        public Preference__c preObj {get;set;}
        public String contactId {get;set;}
        public String preferenceId {get;set;}
        public DonorDetailsController()
        {
            User oUser = [Select Id, ContactId From User Where Id=:UserInfo.getUserId()];
            contactId = oUser.contactId;
            preObj = new Preference__c();                
            getAllCommitmentDetails();
            getAllPaymentDetails();
        }   
        public class CommitmentDetails
        { 
            public String childName {get;Set;}
            public String projectName {get;set;}
            public String commitmentType {get;set;}
            public String commitmentStartDate {get;set;}
            public String commitmentEndDate {get;set;}
            public String perferenceId {get;set;}
            public String childId {get;set;}
        }

        public class PaymentDetails
        {
            public Double amount {get;set;}
            public Double opportunityAmount {get;set;}
            public String paymentMode {get;set;}
            public String paymentFrequency {get;set;}
            public Date paymentStartDate {get;set;}
            public Date paymentEndDate {get;set;}
            public String paymentStatus{get;set;}
        }
        public void getAllCommitmentDetails()
        {
            commitmentDetailsList = new List<CommitmentDetails>(); 
            for (Commitment__c oCommitment : [Select Id, Child__c, Child__r.Name, Start_Date__c, Project__c, 
                                                                    Project__r.Name, Commitment_Type__c, End_Date__c,
                                                                    Preference__c, Status__c From Commitment__c Where Contact__c=:contactId])
                                                                     
           //System.debug(oCommitment);
            {
                CommitmentDetails oCommitmentDetails = new CommitmentDetails();
                oCommitmentDetails.childName = oCommitment.Child__r.Name;
                oCommitmentDetails.projectName = oCommitment.Project__r.Name;
                oCommitmentDetails.commitmentType = oCommitment.Commitment_Type__c;
                oCommitmentDetails.commitmentStartDate = oCommitment.Start_Date__c != null ? oCommitment.Start_Date__c.format() : '';
                oCommitmentDetails.commitmentEndDate = oCommitment.End_Date__c != null ? oCommitment.End_Date__c.format() : ''; 
                oCommitmentDetails.perferenceId = oCommitment.Preference__c;
                oCommitmentDetails.childId = oCommitment.Child__c;
                commitmentDetailsList.add(oCommitmentDetails);
                
            }  
           
            
        }
        public void getAllPaymentDetails()
       {
            paymentDetailsList = new List<PaymentDetails>();
            String opportunityId = [Select OpportunityId From OpportunityContactRole Where ContactId=:contactId limit 1].OpportunityId;
            for (Payment_Schedule__c obj : [Select Amount__c, Payment_End_Date__c, Opportunity__r.Amount, 
                                                                      Payment_Frequency__c, Payment_Mode__c, Payment_Start_Date__c
                                                             From Payment_Schedule__c Where Opportunity__c=:opportunityId])
            {
                PaymentDetails oPaymentDetails = new PaymentDetails();
                oPaymentDetails.amount = obj.Amount__c;
                oPaymentDetails.opportunityAmount = obj.Opportunity__r.Amount;
                oPaymentDetails.paymentMode = obj.Payment_Mode__c;
                oPaymentDetails.paymentFrequency = obj.Payment_Frequency__c;
                oPaymentDetails.paymentStartDate = obj.Payment_Start_Date__c;
                oPaymentDetails.paymentEndDate = obj.Payment_End_Date__c;   
                paymentDetailsList.add(oPaymentDetails);
            }
       }
       public void loadPreference() 
      {
          preObj = [Select Id, Age_From__c, Age_To__c, Sex__c, 
                                    Continent__c, Country__c, Language__c, Religion__c
                                    From Preference__c Where Id=:preferenceId];
          System.debug( preObj  + ' == ' );                                     

      }
 Thanks in advance :)