Below are 3 classes connected to each other. Help me to write a TEST CLASS.

public class IND_NeSLAgreementStatusRequest extends ParentAPIRequest{
public string Deal_No {get;set;}
public IND_NeSLAgreementStatusRequest(Applicant__c app,String loanAppId){

this.Deal_No = 'RJG01179D';//app.Opportunity__r.Parent_Deal_number__c;
validate(System.Label.NeSLAgreementStatus);
}

public override Map<String,String> getHttpRequestHeaders(){
Map<String,String> requestHeaderMap = Utilities.getHeaders();
return requestHeaderMap;
}

public override boolean validate(String serviceName){
if(this.Deal_No == null && String.isBlank(this.Deal_No)){
throw new IND_Exception(System.Label.deal_Number);
}
return true;
}
}


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public class IND_NeSLAgreementStatusService {

public static IND_NeSLAgreementStatusRequest getNeSLAgreementStatusRequest(Applicant__c app,String loanAppId){
try{
IND_NeSLAgreementStatusRequest neSLAgreementStatusRequest = new IND_NeSLAgreementStatusRequest(app,loanAppId);//only validation and setting headers
return neSLAgreementStatusRequest;
}
catch(Exception ex){
ErrorLoggerUtil.logErrorEvent('IND_NeSLAgreementStatusRequest', 'getNeSLAgreementStatusRequest', System.Label.Apex, ex,loanAppId);
throw new IND_Exception(ex.getMessage());
}
}
}
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public class IND_NeSLAgreementStatusResponse extends ParentAPIResponse {

public class Response {
public String status;
public String respDesc;
public List<Content> content;
}

public Response response;

public class Content {
public String Status_Code;
public String Status_Description;
public String Esign_Link;
}

}