on Post -System.CalloutException on one object but not on another

Question

I'm building an application which sends a post request to an endpoint when a particular record is inserted.

The trigger looks like this(for testing purposes):

trigger NotifyPlayersOfShowCancelation on Submittal__c (before insert) {
HttpUtility.sendHttpPostRequest('test.com','some data', null);
return;}

Here is sendHttpPostRequest:

    @future(callout=true)
public static void sendHttpPostRequest(string url, string postData, Map<string,string> headers)
{
    Http h = new Http();
    HttpResponse res = new HttpResponse();
    HttpRequest req = new HttpRequest();
    req.setEndpoint(url);
    req.setMethod('POST');
    if(headers != null)
    {
        for(string key:headers.keySet())
        {
            req.setHeader(key,headers.get(key));
        }
    }
    req.setTimeout(2000); //2 seconds
    req.setBody(postData);
    res = h.send(req);
    system.debug('sent post request successfully');
}

Now let's get to the weird part. every time I try and test the trigger with a test class:

    Test.startTest();
    Test.setMock(HttpCalloutMock.class, new MockHttpResponseGenerator());
    insert sub;
    Test.stopTest();

I get this exception: System.CalloutException: You have uncommitted work pending. Please commit or rollback before calling out.

From my research, it appears this error is thrown when you try and do a DML action and then do a callout afterwards.

When I copy and paste the trigger onto a different object and test that, it completes perfectly fine.

I've removed every trigger for Submittal__c besides my test one, yet the error persists. I do have workflow actions for Submittal__c that changes certain fields on insert, but according to this:

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_triggers_order_of_execution.html

The trigger should execute way before it gets to the workflow rules. Any suggestions?

Answer 1

For future visitors:

It was in fact the workflow updates that were making the error occur.