Mocking ExecutorService to Run Synchronously

Earlier I wrote about a technique for executing code synchronously in an ExecutorService. Here's an alternate approach that uses the Mockito framework to accomplish the same result, but without requiring any supporting code.

                ExecutorService executorService = Mockito.mock(ExecutorService.class);

                

                Mockito.when(executorService.submit(Mockito.argThat(new ArgumentMatcher<Runnable>() {

                    @Override

                    public boolean matches(Object argument) {

                        Runnable runnable = (Runnable) argument;

                        try {

                            runnable.run();

                        } catch (Exception e) {

                            e.printStackTrace();

                            Assert.fail();

                        }

                        return true;

                    }

                }))).thenReturn(Mockito.mock(Future.class));

When a Runnable is submitted to the ExecutorService, the mock simply calls the run method, no threads involved. This can also be adapted for use with Callable for a bit more sophistication. Now just inject the ExecutorService and invoke the code