<apex:page controller="TestBatchFiringController">
</apex:page>

public class TestBatchFiringController {
    public TestBatchFiringController() {
        // These statements successfully completed.

        // Results in a valid AsyncApexJob id, but batch does not execute.
        // AsyncApexJob Id is not valid after method executes (but it is in test context!)
        System.debug('My job id is: ' + Database.executeBatch(new TestBatchFiringBatch(), 1));

        // Results in a valid CronTrigger id, but schedulable does not execute.
        // CronTrigger Id is not valid after method executes (but it is in test context!)
        System.debug('My schedulable job id is ' + System.schedule('Test Job', '20 30 8 10 2 ?', new TestSchedulableFiring()));

        // This would fail with a `LimitException` - DML is not allowed.
        // Account a = new Account(Name = 'Testy Test Test');
        // insert a;
        // System.debug('My Account's Id is ' + a.Id);

        // Setting a savepoint is DML-equivalent - this also throws a `LimitException`
        // System.Savepoint sp = Database.setSavepoint();

    }
}