### Question:
Repeater implements Callable<Boolean> { public Repeater repeat() { return repeat(Callables.returning(null)); } Repeater();  Repeater(String description); static Repeater create(); static Repeater create(String description); Repeater repeat(); Repeater repeat(Runnable body); Repeater repeat(Callable<?> body); Repeater every(long period, TimeUnit unit); Repeater every(Duration duration); Repeater every(groovy.time.Duration duration); Repeater delayOnIteration(Function<? super Integer,Duration> delayFunction); Repeater backoff(final Duration initialDelay, final double multiplier, @Nullable final Duration finalDelay); Repeater backoffTo(final Duration finalDelay); Repeater until(Callable<Boolean> exitCondition); Repeater until(final T target, final Predicate<T> exitCondition); Repeater rethrowException(); Repeater rethrowExceptionImmediately(); Repeater suppressWarnings(); Repeater limitIterationsTo(int iterationLimit); Repeater limitTimeTo(long deadline, TimeUnit unit); Repeater limitTimeTo(Duration duration); boolean run(); void runRequiringTrue(); ReferenceWithError<Boolean> runKeepingError(); String getDescription(); Duration getTimeLimit(); @Override Boolean call(); static final Duration DEFAULT_REAL_QUICK_PERIOD; }### Answer:
@Test public void repeatSucceedsIfClosureIsNonNull() { new Repeater("repeatSucceedsIfClosureIsNonNull").repeat(Callables.returning(true)); }