Merge #17378: TestShell: Fix typos & implement cleanups

2493770 TestShell: Return self from setup() (James Chiang)
a8dea45 TestShell: Simplify default setting of num_nodes (James Chiang)
9c7806e Doc: Remove backticks in test-shell.md code block (James Chiang)
d3ed06e TestShell: Fix typo in TestShell warning printout (James Chiang)

Pull request description:

  This PR follows up on #17288 and fixes typos and implements code clean-ups suggested by reviewers of 19139ee.

  - Typo in `test_shell.py` warning
  - Typo in `test-shell.md` code block
  - Simplified default setting of `num_nodes` in `TestShell.setup()`
  - Enable initializer chaining: `TestShell().setup()`

ACKs for top commit:
  MarcoFalke:
    ACK 2493770
  instagibbs:
    tACK bitcoin/bitcoin@2493770
  jnewbery:
    utACK 2493770

Tree-SHA512: 8fa7c2c550dbc3ec899de9dc328cd55cfa6daafe3b888aa5427e72fea69f064d938ec68e15bfa57109c0f6c3583e627ac4bd69303a11575d056941bd253adee0

Author: MarcoFalke

test/functional/test-shell.md

@@ -31,7 +31,7 @@ importing the `TestShell` class from the `test_shell` sub-package.
 ```
 >>> import sys
 >>> sys.path.insert(0, "/path/to/bitcoin/test/functional")
->>> from test_framework.test_shell import `TestShell`
+>>> from test_framework.test_shell import TestShell
 ```
 
 The following `TestShell` methods manage the lifetime of the underlying bitcoind
@@ -51,8 +51,7 @@ The following sections demonstrate how to initialize, run, and shut down a
 ## 3. Initializing a `TestShell` object
 
 ```
->>> test = TestShell()
->>> test.setup(num_nodes=2, setup_clean_chain=True)
+>>> test = TestShell().setup(num_nodes=2, setup_clean_chain=True)
 20XX-XX-XXTXX:XX:XX.XXXXXXX TestFramework (INFO): Initializing test directory /path/to/bitcoin_func_test_XXXXXXX
 ```
 The `TestShell` forwards all functional test parameters of the parent
@@ -66,8 +65,7 @@ temporary folder. If you need more bitcoind nodes than set by default (1),
 simply increase the `num_nodes` parameter during setup.
 
 ```
->>> test2 = TestShell()
->>> test2.setup()
+>>> test2 = TestShell().setup()
 TestShell is already running!
 ```
 

test/functional/test_framework/test_shell.py

@@ -29,8 +29,7 @@ def setup(self, **kwargs):
 
             # Num_nodes parameter must be set
             # by BitcoinTestFramework child class.
-            self.num_nodes = kwargs.get('num_nodes', 1)
-            kwargs.pop('num_nodes', None)
+            self.num_nodes = 1
 
             # User parameters override default values.
             for key, value in kwargs.items():
@@ -43,6 +42,7 @@ def setup(self, **kwargs):
 
             super().setup()
             self.running = True
+            return self
 
         def shutdown(self):
             if not self.running:
@@ -53,7 +53,7 @@ def shutdown(self):
 
         def reset(self):
             if self.running:
-                print("Shutdown TestWrapper before resetting!")
+                print("Shutdown TestShell before resetting!")
             else:
                 self.num_nodes = None
                 super().__init__()