### Question:
FIFOIdleConnectionsHolder extends IdleConnectionsHolder<W, R> { @Override public Observable<PooledConnection<R, W>> peek() { return peekObservable; } FIFOIdleConnectionsHolder(); @Override Observable<PooledConnection<R, W>> poll(); @Override Observable<PooledConnection<R, W>> peek(); @Override void add(PooledConnection<R, W> toAdd); @Override boolean remove(PooledConnection<R, W> toRemove);  }### Answer:
@Test(timeout = 60000) public void testPeek() throws Exception { holderRule.peekNow(); @SuppressWarnings("unchecked") final PooledConnection<String, String> mock = Mockito.mock(PooledConnection.class); Mockito.when(mock.isUsable()).thenReturn(true); PooledConnection<String, String> added = holderRule.addAConnection(); holderRule.peekNow(added); holderRule.peekNow(added); }