JarCastingtea-time
What is it
A collection of test friendly implementations of time for Java 8
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Executor
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ScheduledExecutorService
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Clock as an interface
This allows the developer to test code that uses ScheduledExecutorService without starting up threads, and control the passage of time properly.
It doesn't just execute the Runnables synchronously, as this gives a false impression of the ordering of events in the system - if you do this, a get() right after a submit() will always work in tests, but never under a real ScheduledExecutorService
Clock
How to use
Don't use the java 8 clock in your code, you cannot control the passage of time properly
Use a tea-time Clock.
How to use in tests
Clock clock = TickingClock.atUTC("2017/10/02 10:23:44.000")
MyClass myClass = new MyClass(clock);
myClass.recordTimestamp();
clock.timePasses(Duration.ofSeconds(23));
myClass.recordTimestamp();
SimpleExecutorServices
You can pretty much replace any usage of ScheduledExecutorService with a SimpleScheduledExecutorService, then use a ControllableSimpleScheduledExecutorService in your code like this
How to use in tests
ControllableSimpleScheduledExecutorService service = new ControllableSimpleScheduledExecutorService();
MyClass myClass = new MyClass(service);
myClass.doSomething(); // schedules a task...
// assert nothing happened yet
service.timePasses(Duration.ofHours(1));
// assert what should have happened.
How to use for real
ScheduledExecutorService service = Executors....();
MyClass myClass = new MyClass(SimpleExecutorServices.wrapping(service));
