To successfully execute the test class for the Queueable classes, the developer should do the following:
Ensure the running user of the test class has the View All permission on the Order object. This is because the OrderQueueableJob class queries the Order object and updates its status. Without the View All permission, the test class may fail due to insufficient access rights or data visibility issues.
Enclose System.enqueueJob(new OrderQueueableJob()) within Test.startTest() and Test.stopTest(). This is because the Queueable jobs are executed asynchronously, and the Test.stopTest() method ensures that all asynchronous processes are completed before the test method finishes. This way, the test class can verify the results of the Queueable job execution.