CODEWITHSUNDEEP
javaunit-testingjunitmockitoguava
Pat Lee
Pat Lee

Reputation: 1

Guava LoadingCache: How to unit test ListenableFuture within CacheLoader

I'm using the Guava LoadingCache like this:

@Inject
private ExecutorService executorService;

private LoadingCache<CacheKey, ResponseEntity<String>> constructCache() {
    return CacheBuilder.newBuilder()
        .maximumSize(100)
        .expireAfterWrite(15, TimeUnit.MINUTES)
        .build(
            new CacheLoader<CacheKey, ResponseEntity<String>>() {
                @Override
                public ResponseEntity<String> load(CacheKey cacheKey) throws Exception {
                    return loadResource(cacheKey);
                }
                @Override
                public ListenableFuture<ResponseEntity<String>> reload(final CacheKey cacheKey, ResponseEntity<String> old) {
                    ListenableFutureTask<ResponseEntity<String>> task = ListenableFutureTask.create(new Callable<ResponseEntity<String>>() {
                        @Override
                        public ResponseEntity<String> call() throws Exception {
                            // this line here!
                            return loadResource(cacheKey);
                        }
                    });
                    executorService.execute(task);
                    return task;
                }
            }
        );
}

private ResponseEntity<String> loadResource(CacheKey cacheKey) {
    // ...
    // external call
    // ...
}

I can test every line except one. How do I unit test the line return loadResource(cacheKey) within the Runnable task? Right now I'm mocking the executorService in order to make sure the asynchronous refresh is really taking place.

Upvotes: 0

Views: 2979

Answers (2)

Frank Pavageau
Frank Pavageau

Reputation: 11725

Instead of mocking the ExecutorService, you can use the sameThreadExecutor so the task is immediately executed.

Upvotes: 2

John B
John B

Reputation: 32969

If you are mocking the ExecutorService, use an ArgumentCaptor to get the ListenableFutureTask that was passed. Execute the call method on the task and verify that loadResource was called.

Upvotes: 0

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