Hi venkat,

You have to make some changes to your controller then after write test class. below is the changed code whose code coverage is 93%.

Apex class:

public Account retrieveOrganisation(String orgId) {        
        Account retOrg = new Account();
        String strQuery = 'SELECT ';
        Map<String, Schema.sObjectField> mpFields = Schema.sObjectType.Account.fields.getMap();
        Set<String> geoFieldPrefixes = new Set<String>();
        for (Schema.sObjectField fld: mpFields.values()) if (fld.getDescribe().getName().contains('Longitude') || fld.getDescribe().getName().contains('Latitude')) geoFieldPrefixes.add(fld.getDescribe().getName().split('__',2)[0]);
        for (Schema.sObjectField fld: mpFields.values()) {
            String fldName=fld.getDescribe().getName();
            if (!geoFieldPrefixes.contains(fldName.split('__',2)[0])) strQuery+=fldName+',';
        }
        if (strQuery.endsWith(',')) strQuery = strQuery.substring(0, strQuery.length() - 1);
        strQuery+=' FROM Account WHERE Id=\''+orgId+'\' LIMIT 1';
        System.debug('### OUTPUT >>>>> retrieveOrganisation: strQuery: '+strQuery);
        List<Account> lstAccount = Database.query(strQuery);
        if(lstAccount.size() > 0){
            retOrg = lstAccount[0];
        }
        return retOrg;
    }

 Test class:

@istest
public class Testctrlmadetestclass{
    Private Static testmethod void Testctrlmadetestclass(){
        YourclassName objYourclassName = new YourclassName();
        objYourclassName.retrieveOrganisation(UserInfo.getOrganizationId());
    }
}

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Thanks,
Hitesh Patel
SFDC Certified Developer & Administrator