### Question:
QuotaServer { public double acquire(T operation) { checkArgument(quotaMap.containsKey(operation), "undefined operation"); return quotaMap.get(operation).acquire(); } private  QuotaServer(Builder<T, ? extends QuotaServer<T>> builder); double acquire(T operation); double getRate(T operation); static QuotaServer<T> createFromConfiguration(
      String quotaPrefix, Class<T> enumClass); static final double DEFAULT_QPS; }### Answer:
@Test public void testInvalidOperationAcquire() { QuotaServer<Operations> qs = new QuotaServer.Builder<>(Operations.class).build(); thrown.expect(IllegalArgumentException.class); qs.acquire(null); }