Test that node input is not all zeros

[hunse]

I've added a test to make sure that the node input is not all zeros when copying off the board.

@mundya @tcstewar: This is the problem I was getting yesterday. It came up again today, even using my new IP settings. I realized yesterday that @tcstewar's original suggested IP settings should have worked (this is basically what I put in the README, I think), but for some reason they didn't. Though they did seem to work when I went back to them after getting the board working with the other settings. All very strange.

Anyway, this test should at least let users know if this is happening. It's kind of slow, though, I guess because it spools up a simulator? Maybe it can be re-written to more specifically test the problem.

We'll have to spend more time at some point trying to figure out why this occurs, and whether we can have better IP suggestions to avoid it.

[tcstewar]

Hmm... when it came up again today, did it continue to be a problem even when the model was run for a long time (20+ seconds)?

We have sometimes seen this happen briefly at the beginning of a run, but goes away after a ten seconds.

I'd thought the problem that we fixed before was due to the gateway setting, which should have been left blank, but you'd said you set to the same IP address as the board.

[hunse]

I think you gave me some settings first, that had the gateway empty. It was when I used Ian's settings that I had the gateway set.

I didn't run it for a long time, so maybe it was just due to run length. But when I changed the IP, it seemed to work immediately, which suggests it's IP related. I'll play around more.

[mundya]

Sorry for the huge delay in getting back to you on this. Would you be happy for me to make this code a utility that a user can be expected to call rather than have it sit in the tests?

[hunse]

Sure, that could work.