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Functional tests

Writing Functional Tests

Example test

The is a heavily commented example of a test case that uses both the RPC and P2P interfaces. If you are writing your first test, copy that file and modify to fit your needs.


Running with the --coverage argument tracks which RPCs are called by the tests and prints a report of uncovered RPCs in the summary. This can be used (along with the --extended argument) to find out which RPCs we don’t have test cases for.

Style guidelines

  • Where possible, try to adhere to PEP-8 guidelines
  • Use a python linter like flake8 before submitting PRs to catch common style nits (eg trailing whitespace, unused imports, etc)
  • Avoid wildcard imports where possible
  • Use a module-level docstring to describe what the test is testing, and how it is testing it.
  • When subclassing the BitcoinTestFramwork, place overrides for the set_test_params(), add_options() and setup_xxxx() methods at the top of the subclass, then locally-defined helper methods, then the run_test() method.

General test-writing advice

  • Set self.num_nodes to the minimum number of nodes necessary for the test. Having additional unrequired nodes adds to the execution time of the test as well as memory/CPU/disk requirements (which is important when running tests in parallel or on Travis).
  • Avoid stop-starting the nodes multiple times during the test if possible. A stop-start takes several seconds, so doing it several times blows up the runtime of the test.
  • Set the self.setup_clean_chain variable in set_test_params() to control whether or not to use the cached data directories. The cached data directories contain a 200-block pre-mined blockchain and wallets for four nodes. Each node has 25 mature blocks (25x50=1250 BTC) in its wallet.
  • When calling RPCs with lots of arguments, consider using named keyword arguments instead of positional arguments to make the intent of the call clear to readers.

RPC and P2P definitions

Test writers may find it helpful to refer to the definitions for the RPC and P2P messages. These can be found in the following source files:

  • /src/rpc/* for RPCs
  • /src/wallet/rpc* for wallet RPCs
  • ProcessMessage() in /src/net_processing.cpp for parsing P2P messages

Using the P2P interface

  • contains all the definitions for objects that pass over the network (CBlock, CTransaction, etc, along with the network-level wrappers for them, msg_block, msg_tx, etc).

  • P2P tests have two threads. One thread handles all network communication with the bitcoind(s) being tested (using python’s asyncore package); the other implements the test logic.

  • NodeConn is the class used to connect to a bitcoind. If you implement a callback class that derives from NodeConnCB and pass that to the NodeConn object, your code will receive the appropriate callbacks when events of interest arrive.

  • Call NetworkThread.start() after all NodeConn objects are created to start the networking thread. (Continue with the test logic in your existing thread.)

  • Can be used to write tests where specific P2P protocol behavior is tested. Examples tests are,


  • Comptool is a Testing framework for writing tests that compare the block/tx acceptance behavior of a bitcoind against 1 or more other bitcoind instances. It should not be used to write static tests with known outcomes, since that type of test is easier to write and maintain using the standard BitcoinTestFramework.

  • Set the num_nodes variable (defined in ComparisonTestFramework) to start up 1 or more nodes. If using 1 node, then --testbinary can be used as a command line option to change the bitcoind binary used by the test. If using 2 or more nodes, then --refbinary can be optionally used to change the bitcoind that will be used on nodes 2 and up.

  • Implement a (generator) function called get_tests() which yields TestInstances. Each TestInstance consists of:

    • A list of [object, outcome, hash] entries
    • object is a CBlock, CTransaction, or CBlockHeader. CBlock’s and CTransaction’s are tested for acceptance. CBlockHeaders can be used so that the test runner can deliver complete headers-chains when requested from the bitcoind, to allow writing tests where blocks can be delivered out of order but still processed by headers-first bitcoind’s.
    • outcome is True, False, or None. If True or False, the tip is compared with the expected tip -- either the block passed in, or the hash specified as the optional 3rd entry. If None is specified, then the test will compare all the bitcoind’s being tested to see if they all agree on what the best tip is.
    • hash is the block hash of the tip to compare against. Optional to specify; if left out then the hash of the block passed in will be used as the expected tip. This allows for specifying an expected tip while testing the handling of either invalid blocks or blocks delivered out of order, which complete a longer chain.
    • sync_every_block: True/False. If False, then all blocks are inv’ed together, and the test runner waits until the node receives the last one, and tests only the last block for tip acceptance using the outcome and specified tip. If True, then each block is tested in sequence and synced (this is slower when processing many blocks).
    • sync_every_transaction: True/False. Analogous to sync_every_block, except if the outcome on the last tx is “None”, then the contents of the entire mempool are compared across all bitcoind connections. If True or False, then only the last tx’s acceptance is tested against the given outcome.
  • For examples of tests written in this framework, see and

test-framework modules


Taken from the python-bitcoinrpc repository.


Base class for functional tests.


Generally useful functions.


Basic code to support P2P connectivity to a bitcoind.


Framework for comparison-tool style, P2P tests.


Utilities for manipulating transaction scripts (originally from python-bitcoinlib)


Implements disk-backed block and tx storage.


Wrapper around OpenSSL EC_Key (originally from python-bitcoinlib)


Helpers for


Helper functions for creating blocks and transactions.