@Test public void onErrorResumeNextFunctionReturnsNull() { try { error.onErrorResumeNext(new Function<Throwable, Single<Integer>>() { @Override public Single<Integer> apply(Throwable e) { return null; } }).blockingGet(); } catch (CompositeException ex) { assertTrue(ex.toString(), ex.getExceptions().get(1) instanceof NullPointerException); } }