Bitcoin Core: Test The Test

The goal of these exercises is to learn the Bitcoin Core development environment through the Bitcoin Test Framework.

Set Up

1. Clone the Bitcoin Core repository
2. Checkout the v27.1 tag (commit 1088a98f5aad080cc6cca2da174f206509fcda6c)
3. Build Bitcoin Core
   • The docs in the repo should provide sufficient guidance for this
   • If you have any problems, search the issues on GitHub or try Bitcoin Stack Exchange
   • Recommended minimal configure options:
     • ./configure --disable-bench --disable-fuzz-binary --enable-debug --without-gui --enable-suppress-external-warnings
4. Run all the functional tests
   • All tests should pass! (You can ignore "skipped" tests)
   • You may be able to speed up the test suite using a RAM disk

Challenge

1. Choose a target test from https://github.com/bitcoin/bitcoin/tree/1088a98f5aad080cc6cca2da174f206509fcda6c/test/functional
2. Write a minimal commit in src/ (*.cpp or *.h files only) that makes this one single test fail, and no others!
   • You can ignore "skipped" tests
3. Submit your commit as a diff using git show <commit hash>

• You do NOT need to run the unit tests or the extended tests (test_runner --extended) for this exercise.

Example

Target test

test/functional/feature_abortnode.py

Commit

commit 14683cab0e91f1e7984c61fb4b8b74574fb4b339
Author: Matthew Zipkin <pinheadmz@gmail.com>
Date:   Sat Dec 30 13:04:24 2023 +0000

    make feature_abortnode.py fail

diff --git a/src/validation.cpp b/src/validation.cpp
index a6cab6b095..df093c9c34 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -3115,7 +3115,7 @@ bool Chainstate::ActivateBestChainStep(BlockValidationState& state, CBlockIndex*
             // If we're unable to disconnect a block during normal operation,
             // then that is a failure of our local system -- we should abort
             // rather than stay on a less work chain.
-            FatalError(m_chainman.GetNotifications(), state, "Failed to disconnect block; see debug.log for details");
+            // FatalError(m_chainman.GetNotifications(), state, "Failed to disconnect block; see debug.log for details");
             return false;
         }
         fBlocksDisconnected = true;

Submit this diff as a file (e.g. break_feature_abortnode.diff) in your classroom repository.

Functional test results

Example output (truncated):

...
wallet_txn_doublespend.py --mineblock                  | ✓ Passed  | 3 s
wallet_watchonly.py --legacy-wallet                    | ✓ Passed  | 3 s
wallet_watchonly.py --usecli --legacy-wallet           | ✓ Passed  | 3 s
...
wallet_backwards_compatibility.py --legacy-wallet      | ○ Skipped | 0 s
wallet_inactive_hdchains.py --legacy-wallet            | ○ Skipped | 0 s
wallet_upgradewallet.py --legacy-wallet                | ○ Skipped | 0 s
feature_abortnode.py                                   | ✖ Failed  | 6 s

ALL                                                    | ✖ Failed  | 4009 s (accumulated) 
Runtime: 714 s