Testing Queueable Apex
To test Queueable Apex, we follow the same pattern we have used for all our asynchronous code. We place the System.enqueueJob call between a Test.startTest method call and a Test.stopTest method call to run the asynchronous process synchronously:
@isTest
private class ExampleQueueable_Test {
@isTest
private static void testExecute() {
Test.startTest();
System.enqueueJob(new ExampleQueueable());
Test.stopTest();
//Assert on expected changes
}
}
Note that if you were to run the following code:
@isTest
private class ExampleQueueable_Test {
    @isTest
    private static void testExecute() {
          Test.startTest();
          Id apexJobId = System.enqueueJob(new           ExampleQueueable());
          ...
