Merge #11023: [tests] Add option to attach a python debugger if functional test fails

cc5d38f4b Add option to attach a python debugger if test fails (John Newbery)

Pull request description:

  Adds a simple option to the test_framework to attach pdb if the test fails.

  Helpful for catching and debugging intermittent failures: Run the test in a loop with this option. The first failure will cause execution to pause and nodes will be left running for interactive debugging.

  @sdaftuar

Tree-SHA512: 01cfae15fa3f04ed6ec6a99fef60a6c6a59723429309e81eacd6767caf12f5758f59b337804291ecab33a38a2958f36e2b513d201bee72a2eeb207a67046f952

test/functional/test_framework/test_framework.py

@@ -11,6 +11,7 @@ import http.client
 import logging
 import optparse
 import os
+import pdb
 import shutil
 import subprocess
 import sys
@@ -125,6 +126,8 @@ class BitcoinTestFramework(object):
                           help="Write tested RPC commands into this directory")
         parser.add_option("--configfile", dest="configfile",
                           help="Location of the test framework config file")
+        parser.add_option("--pdbonfailure", dest="pdbonfailure", default=False, action="store_true",
+                          help="Attach a python debugger if test fails")
         self.add_options(parser)
         (self.options, self.args) = parser.parse_args()
 
@@ -162,6 +165,10 @@ class BitcoinTestFramework(object):
         except KeyboardInterrupt as e:
             self.log.warning("Exiting after keyboard interrupt")
 
+        if success == TestStatus.FAILED and self.options.pdbonfailure:
+            print("Testcase failed. Attaching python debugger. Enter ? for help")
+            pdb.set_trace()
+
         if not self.options.noshutdown:
             self.log.info("Stopping nodes")
             if self.nodes: