private String subscribe() throws Throwable { TestContext ctx = testCreate(2); subscriptionManager.setCompletionHandler((e) -> { if (e != null) { ctx.failIteration(e); return; } ctx.completeIteration(); }); final String[] subscriptionId = new String[1]; subscriptionManager.start(handler(), (id) -> { subscriptionId[0] = id; ctx.completeIteration(); }); testWait(ctx); // reset completion handler subscriptionManager.setCompletionHandler(null); return subscriptionId[0]; }