Hello all,
I am having trouble with an HTTP Callout Test. I have a Trigger which sends it's info to the Class which houses the Http Callout. To Test for an Http Callout I followed the Apex Dev documentation (https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_restful_http_testing_httpcalloutmock.htm) where I create two Test classes, one sends Mock Http info and the other calls the Mock info. I beleive the problem is in the passing the "String ldid" from the Trigger to the Class. Trigger/Class/Tests below. Any ideas on how to solve this? Thanks!
Trigger:

String ldid;       
if(Trigger.isBefore){
      if(Trigger.isUpdate || Trigger.isInsert){
          for(Lead ld : Trigger.new){
              if(ld.IsConverted == TRUE && ld.Segment__c == 'Large Group'){
                  ldid = ld.Id;
                  CallApply.basicAuthCallout(ldid);

Class:

public class CallApply {
    public static HttpResponse basicAuthCallout(String ldid){
        HttpRequest req = new HttpRequest();
        req.setEndpoint('https://test');
        req.setMethod('POST');
        String body = '{"LeadId":"'+ldid+'"}';
        req.setHeader('Content-Type','application/json');  
        req.setBody(body);
        Http http = new Http();
        HTTPResponse res = http.send(req);
        return res;
    }
}

Test1:

@isTest
global class Test_callApply1 implements HttpCalloutMock {
    global HTTPResponse respond(HttpRequest req) {
        HttpResponse res = new HttpResponse();
        res.setHeader('Content-Type','application/json');
        res.setBody('{"example":"test"}');
        res.setStatusCode(200);
        return res;
    }
}

Test2:

@isTest
private class Test_callApply2 {
     @isTest static void testCallout() {
        Test.setMock(HttpCalloutMock.class, new Test_callApply1());
        //create Lead to pass value 'ldid'
        Lead ld = new Lead();
        ld.FirstName = 'testRyan';
        ld.LastName = 'testGreene';
        ld.email = 'testingtrigger1@test.com';
        ld.Company = 'testCompanyasdasdasdeyjhlnn';
        insert ld;
        String ldid = ld.id;
         
        HttpResponse res = CallApply.basicAuthCallout(ldid);
        
        String contentType = res.getHeader('Content-Type');
        System.assert(contentType == 'application/json');
        String actualValue = res.getBody();
        String expectedValue = '{"example":"test"}';
        System.assertEquals(actualValue, expectedValue);
        System.assertEquals(200, res.getStatusCode());
    }
}