Merge #11121: TestNode tidyups

7148b74dc [tests] Functional tests must explicitly set num_nodes (John Newbery)
5448a1471 [tests] don't override __init__() in individual tests (John Newbery)
6cf094a02 [tests] Avoid passing around member variables in test_framework (John Newbery)
36b626867 [tests] TestNode: separate add_node from start_node (John Newbery)
be2a2ab6a [tests] fix - use rpc_timeout as rpc timeout (John Newbery)

Pull request description:

  Some additional tidyups after the introduction of TestNode:

  - commit 1 makes TestNode use the correct rpc timeout. This should have been included in #11077
  - commit 2 separates `add_node()` from `start_node()` as originally discussed here: https://github.com/bitcoin/bitcoin/pull/10556#discussion_r121161453 with @kallewoof . The test writer no longer needs to assign to `self.nodes` when starting/stopping nodes.
  - commit 3 adds a `set_test_params()` method, so individual tests don't need to override `__init__()` and call `super().__init__()`

Tree-SHA512: 0adb030623b96675b5c29e2890ce99ccd837ed05f721d0c91b35378c5ac01b6658174aac12f1f77402e1d38b61f39b3c43b4df85c96952565dde1cda05b0db84

test/functional/test_framework/test_node.py

@@ -65,9 +65,13 @@ class TestNode():
         assert self.rpc_connected and self.rpc is not None, "Error: no RPC connection"
         return self.rpc.__getattr__(*args, **kwargs)
 
-    def start(self):
+    def start(self, extra_args=None, stderr=None):
         """Start the node."""
-        self.process = subprocess.Popen(self.args + self.extra_args, stderr=self.stderr)
+        if extra_args is None:
+            extra_args = self.extra_args
+        if stderr is None:
+            stderr = self.stderr
+        self.process = subprocess.Popen(self.args + extra_args, stderr=stderr)
         self.running = True
         self.log.debug("bitcoind started, waiting for RPC to come up")
 
@@ -78,7 +82,7 @@ class TestNode():
         for _ in range(poll_per_s * self.rpc_timeout):
             assert self.process.poll() is None, "bitcoind exited with status %i during initialization" % self.process.returncode
             try:
-                self.rpc = get_rpc_proxy(rpc_url(self.datadir, self.index, self.rpchost), self.index, coveragedir=self.coverage_dir)
+                self.rpc = get_rpc_proxy(rpc_url(self.datadir, self.index, self.rpchost), self.index, timeout=self.rpc_timeout, coveragedir=self.coverage_dir)
                 self.rpc.getblockcount()
                 # If the call to getblockcount() succeeds then the RPC connection is up
                 self.rpc_connected = True