[test] Add getblockchaininfo functional test

[promag]

Adds functional test for getblockchaininfo. Also deals with the fact that pruneheight is only in the response when pruning is enabled (related to #11366).

[promag]

Should assert values or types of each field?

[jnewbery]

value: only if you're testing a meaningful value
type: I don't think we do this for other RPC methods, so I wouldn't bother

Thinking about this some more, perhaps we can add some utility method check_rpc_return_object(dict) which tests the presence and type of each field in the return object? Obviously not for this PR.

[jnewbery]

concept ACK. Thanks for improving coverage here!

A few nits inline. Nothing blocking this from being merged if you don't want to take them.

[jnewbery]

suggestion: perhaps add `self.log.info("test getblockchaininfo")

[promag]

Done.

[jnewbery]

value: only if you're testing a meaningful value
type: I don't think we do this for other RPC methods, so I wouldn't bother

Thinking about this some more, perhaps we can add some utility method check_rpc_return_object(dict) which tests the presence and type of each field in the return object? Obviously not for this PR.

[jnewbery]

You can speed this test up by starting with pruning the first time, and then restart without pruning (saves one stop-start which is a slow operation). Do that by setting self.extra_args = [['-stopatheight=207', '-prune=1']] in set_test_params() and then setting self.extra_args = [['-stopatheight=207']] before restarting.

[jnewbery]

I think you can just use self.start_node(0). The default will use self.extra_args[0] for its args.

[promag]

Done.

[promag]

Convenient method to stop and start a node with the same arguments as before. If this gets ACK's I can push a commit to use where appropriate or submit this in a separate PR.

[jnewbery]

Great! Ideally the stop and start methods in TestFramework would be methods on the TestNode class, and so would this, but we can clean that up later.

You can change this to:

def restart_node(self, i):
    """Stop and start a test node"""
    self.stop_node(i)
    self.start_node(i)

As long as you also take my change to blockchain.py above.

[jnewbery]

I like the new restart_node() helper function. A couple of comments inline.

[jnewbery]

Sorry, I misled you here. You should use self.nodes[0].extra_args = .... The self.extra_args class variable is only used when instantiating the TestNode. That's important for restart_node()

[jnewbery]

Great! Ideally the stop and start methods in TestFramework would be methods on the TestNode class, and so would this, but we can clean that up later.

You can change this to:

def restart_node(self, i):
    """Stop and start a test node"""
    self.stop_node(i)
    self.start_node(i)

As long as you also take my change to blockchain.py above.

[promag]

@jnewbery added the option to override node.extra_args. I wonder if that this new extra_arg should be saved in node.

[jnewbery]

Looks good. I don't think you need to update node.extra_args

[esotericnonsense]

Noted for #11367, can update to include relevant checks (or vice versa, whichever goes in first I guess)

[promag]

I guess this could go in first since #11367 is a new feature. But if #11367 goes first then I'm happy to update this.

[jnewbery]

Tested ACK f6ffb14

[jnewbery]

@promag @esotericnonsense - I think it's a good idea if you decide between yourselves which should go in first and then rebase the other on top of it (otherwise there's a risk they both get merged independently and no tests are added for #11367)

[esotericnonsense]

I'll rebase on top, given that there seem to be a few niggles with #11367 this one can go in first.