Bitcoin Core: Test The Test

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

Requirements

1. Build Bitcoin Core from the included source code
2. Run the functional tests (all should pass!)
3. Modify the source code such that ONLY ONE functional test FAILS
4. Commit your modified code and push your branch back to GitHub for automatic evaluation

Tip

GITHUB CLASSROOM: Each student will get a private fork of this repository when they join the GitHub Classroom assignment. You will commit and push your submissions to GitHub which will evaluate the answers automatically, like a continuous integration test. You can commit and push as often as you like and GitHub will re-evaluate your code every time.

Set Up

Tip

A copy of the Bitcoin Core codebase is included in this repo in /bitcoin. It was cloned at a specific commit on master branch just after v28.0 was tagged, so it will require the CMAKE build system.

1. 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
2. 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

Example commands after satisfying requirements for your system:

# Only use the code base in this repository
cd bitcoin

# Configure cmake to build as little as possible
cmake -B build \
    -DBUILD_GUI=OFF \
    -DWITH_BDB=OFF  \
    -DBUILD_BENCH=OFF  \
    -DBUILD_FOR_FUZZING=OFF \
    -DBUILD_KERNEL_LIB=OFF \
    -DBUILD_SHARED_LIBS=OFF \
    -DBUILD_TESTS=OFF \
    -DBUILD_TX=OFF \
    -DBUILD_UTIL=OFF \
    -DBUILD_WALLET_TOOL=OFF

# Compile!
cmake --build build -j$(nproc)

# Run the functional tests
build/test/functional/test_runner.py

Challenge

1. Choose a target test from the funcitonal test directory.
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. Commit your changes to this repository and push.

Tip

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

Example

Target test

feature_abortnode

Commit

commit 17f920100af18efae76bb6445f6c5bd970e7a19c
Author: Matthew Zipkin <[email protected]>
Date:   Mon Nov 4 12:46:00 2024 -0500

    make feature_abortnode.py fail

diff --git a/bitcoin/src/block_reader.cpp b/bitcoin/src/block_reader.cpp
index f9288fc..10582f5 100644
--- a/bitcoin/src/block_reader.cpp
+++ b/bitcoin/src/block_reader.cpp
@@ -3333,7 +3333,7 @@ bool BlockReader::ReadBestBlock(BlockValidationState& state, CBlockIndex*
             // Try to read block from disk and increment attempts counter
-            ReadBlock(m_chainman.GetNotifications(), state, ++attempts);
+            ReadBlock(m_chainman.GetNotifications(), state, 0);
             return attempts;
         }
         fBlockRead = true;

Functional test results

Example output (truncated):

...
wallet_txn_doublespend.py --legacy-wallet                | ○ Skipped | 0 s
wallet_upgradewallet.py --legacy-wallet                  | ○ Skipped | 0 s
wallet_watchonly.py --legacy-wallet                      | ○ Skipped | 1 s
wallet_watchonly.py --usecli --legacy-wallet             | ○ Skipped | 1 s
feature_abortnode.py                                     | ✖ Failed  | 6 s

ALL                                                      | ✖ Failed  | 1681 s (accumulated)
Runtime: 454 s

Runtime: 714 s