Test Class - System.CalloutException: You have uncommitted work pending - Platform Event

Firstly, The async Apex will be executed only at point Test.stopTest(). So, when you are moving the EventBus.publish(jobPostingList) line after stopTest, it is never getting executed and so your future callout method will not even be covered in test.

Based on comment from @sfdcfox

I tested this again. It seems future callout from platform event trigger without stopTest is not executing but same future method from account trigger (after insert) is getting invoked without stopTest. (Have to do further testing for different types of objects). However this will not affect the current question in context - You need to check for DMLs in future method before callout.

Note that below test class will run without any problem:

@isTest static void test(){ Test.startTest(); insert new Account(Name='test'); Test.setMock(HttpCalloutMock.class, new AnimalsHttpCalloutMock()); List<Database.SaveResult> results = EventBus.publish(new List<POC_Platform_Event__e>{new POC_Platform_Event__e()}); Test.stopTest(); } 

Although I have callout in Event trigger, above test method will be success. Thats because the actual callout is separated into separate transaction by using future.

However, the moment I introduce DML statement in future method before callout I get the uncommitted error. Below callout will give error:

@future(callout=true) public static void mycallout(){ insert new Account(Name='new test'); Http http = new Http(); HttpRequest request = new HttpRequest(); request.setEndpoint('https://th-apex-http-callout.herokuapp.com/animals'); request.setMethod('GET'); HttpResponse response = http.send(request); } 

When I remove the line insert new Account(Name='new test');, the test class will be success again.

You need to check in your future method if there are DIRECT OR INDIRECT (through other class references/triggers) DMLs happening. There is no prob with your test class.