Apex Class
/*
Having the Utilities of the Askiiris Integration
*/
public without Sharing class Integration_Util {
    Public Static FINAL String DML_ERROR='Error Occured While Saving Record To database';
    /*
Method to log the integration trace in notes
*/
    Public Static void InsertNote(id parentId,string body,string title,boolean isPrivate,boolean ExceptionOccured){
        note resp = new note();
        resp.parentId = parentId; 
        resp.body =body; 
        resp.title = title; 
        resp.isPrivate = isPrivate; 
        database.insert(resp,false); 
    }
     /*
Method to send the Exception Email to CMSO-PS
*/
    public static void sendExceptionEmail(String[] emailId,String subject,String emailBody){
        Messaging.SingleEmailMessage semail = new Messaging.SingleEmailMessage();
        semail.setToAddresses(emailId); 
        semail.setSubject(subject); 
        semail.setHtmlBody(emailBody); 
        Messaging.sendEmail(new Messaging.SingleEmailMessage[] {semail}); 
    } 
    /*
Method to get the Integration Credentials
*/
    Public Static CredentialsWrapper getCredetials( String credentialDevName){
        Integration_Credentials_Mapping__mdt mdt=[select id,Production_End_point_URI__c,Sanbox_End_point_URI__c,
                                                  Sandbox_password__c,Sandbox_user_name__c,Production_password__c,
                                                  Production_user_name__c,security_hns__c,Suffix_URL_1__c,Suffix_URL_2__c,
                                                  Sandbox_Auth_URI__c,Production_Auth_URI__c
                                                  From Integration_Credentials_Mapping__mdt 
                                                  where DeveloperName=:credentialDevName LIMIT 100];
        
        boolean isSandbox=[SELECT issandbox from organization LIMIT 1].isSandbox;
        CredentialsWrapper credwrap=new CredentialsWrapper();
        if(isSandbox){
            credwrap.enpointUrl=mdt.Sanbox_End_point_URI__c;
            credwrap.username =mdt.Sandbox_user_name__c;
            credwrap.password =mdt.Sandbox_password__c;
            credwrap.authTokenUrl =mdt.Sandbox_Auth_URI__c; 
        }else{
            credwrap.enpointUrl=mdt.Production_End_point_URI__c;
            credwrap.username=mdt.Production_user_name__c;
            credwrap.password=mdt.Production_password__c;
            credwrap.authTokenUrl =mdt.Production_Auth_URI__c; 
        }
        credwrap.hnsUrl=mdt.security_hns__c;
        credwrap.isSandbox=isSandbox;
        credwrap.suffixUrl1=mdt.Suffix_URL_1__c;
        credwrap.suffixUrl2=mdt.Suffix_URL_2__c;
        
        return credwrap;
    } 
    /*
Wrapper class used wrap the Integration Credentials
*/
    Public without sharing class CredentialsWrapper{
        Public String username;
        Public String password;
        Public String enpointUrl;
        Public String hnsUrl;
        public Boolean isSandbox;
        Public String suffixUrl1;
        public String suffixUrl2;
        Public String authTokenUrl;
        
    }
    
}

My Test Class

@isTest
public class Integration_Util_UT {

    private static testmethod void InsertNote() {
    Integration_Util.InsertNote('00300000003T2PGAA0','hello','hello',True,True);
     }                    
                    
    private static testmethod void sendExceptionEmail() {
        Integration_Util.sendExceptionEmail('fdgd@df.com','hello','hello');
       }                
                    
    private static testmethod void getCredetials() {
        Integration_Util.getCredetials('hello');
        }                    
}                

My error : "Method does not exist or incorrect signature: void sendExceptionEmail(String, String, String) from the type Integration_Util"
Also the current code coverage is 31%, please hep me to get code coverage 
Thanks in advance